Balancing device for arthroplasty and methods for use

ABSTRACT

A joint balancing insert with an actuated mechanism is for balancing a joint during a joint surgery is disclosed. The joint balancing insert includes a first plate, a second plate and an actuator there between. The second plate includes an integrated mounting portion for mounting a cutting block used to guide surgical cuts of the joint during the joint surgery. Various configurations of the integrated mounting portion may be implemented in the insert to provide for mounting various types of cutting blocks, such as cutting blocks for tibial cuts, femoral cuts, and distal femoral cuts.

RELATED APPLICATION

This application claims the benefit of U.S. provisional patentapplication Ser. No. 62/137,661 entitled “Balancing Device forArthroplasty and Methods of Use,” filed on Mar. 24, 2015, which ishereby incorporated by reference.

FIELD OF THE INVENTION

Various embodiments described herein relate generally to devices andmethods for balancing a joint during prosthetic arthroplasty, and toactuated positioning and sensing devices for positioning prostheticcomponents and balancing a joint during arthroplasty surgery.

BACKGROUND

Arthroplasty involves the repair of a joint by replacing one or moreportions of the joint to eliminate pain and improve movement. Forexample, loss of cartilage or friction between bone surfaces can betreated by inserting an artificial joint, which includes one or moreprostheses designed to replace bone surfaces and cartilage while alsoallowing for a range of movement similar to the original joint.

Knee arthroplasty typically involves resecting (cutting away) thediseased and damaged surfaces of the lower end of the femur (thighbone), the upper end of the tibia (shin bone), and the joint surface ofthe patella (knee cap). These surfaces are then replaced by artificialmaterials. The femoral component or prosthesis is typically made from acobalt chrome alloy and is attached to the femur with fixation devicessuch as pegs, often with the use of bone cement to bond the femoralprosthesis to the underlying bone. The tibial component typicallyconsists of two parts—a metal tray (titanium or cobalt chrome alloy) anda polyethylene insert—that are assembled together during surgery. Themetal tray is fixed to bone with screws, pegs, or a stem; while theinsert is locked into the metal tray and articulates with the femoralcomponent.

The technical challenges in knee arthroplasty are: restoration of thenatural alignment of the knee with respect to the hip and the ankle;regaining the range of motion of the knee; and inducing theartificially-implanted knee to move in a manner similar to a normalknee. These goals are accomplished by making the bone cuts at preciselocations and orientation relative to the rest of the bone, selectingthe appropriate size and shape of the prosthetic components, placing theprostheses at the appropriate location on the bones and with respect toeach other, and selecting an insert of appropriate thickness such thatthe knee joint is neither too lose or too tight.

Despite continuous improvements in the design and manufacture ofartificial joints and in surgical instruments, the actual arthroplastyrelies primarily on the skill and expertise of the surgeon performingthe procedure. Arthroplasty requires that a surgeon not only insert theartificial joint, but also “balance” the joint to ensure that themovement of the artificial joint is as similar as possible to a normalrange of motion. Balancing the joint often requires careful measurementand cutting of bone, ligaments and other tissue, as well as loadbalancing to ensure that the force applied by the bones to the joint isevenly distributed and range of motion testing to determine if theartificial joint is capable of movement in the direction and distancerequired for normal movement. The balancing process often requires thesurgeon to simply physically hold the joint and “feel” whether themovement of the joint and the forces being applied to the joint arecorrect. As a result, the process of balancing the joint is largelysubjective, as it relies upon the experience and knowledge of thesurgeon to understand whether the movement of the artificial joint is“about right.” Misalignment of any of these parameters may result inlimited range of motion of the joint, continued pain at the joint andearly failure of the artificial joint due to excess load distribution orfriction.

To aid in balancing the artificial joint during arthroplasty,measurement devices have been developed which help a surgeon measuresome parameters during the balancing of the joint. The most commonbalancing devices are mechanical in nature: the surgeon manually appliesforce on the device to distract the bones of the joints and the distancebetween the bones is visually measured. Some measurement devicesincorporate sensors which can be inserted into the artificial joint toprovide measurements about load distribution that are useful whenattempting to balance the joint. Even with these measurement devices,the surgeon is still required to manually apply an unknown or inaccurateforce to the joint in order to determine whether the joint is balanced.If the amount of applied force is inconsistent with the actual forceapplied to the joint during actual use, the joint may not moveappropriately and may wear prematurely, leading to limited movement,pain, and eventual replacement or further surgical repairs.

SUMMARY OF THE DISCLOSURE

Disclosed herein are devices and methods for balancing a joint duringsurgical procedures, such as prosthetic arthroplasty. In embodiments,the device is an insert with one or more plates, one or more sensors andat least one actuated mechanism for actuating the device against one ormore parts of the joint. The one or more plates are disposed betweenbone structures which define the joint, such as the femur and the tibiain a knee joint. The one or more sensors provide force, position andangular data about the movement of the joint, which, along with theapplied force data derived from the movement of the actuated mechanism,provide for highly accurate and dynamic adjustments of the joint. In oneembodiment, at least one actuated mechanism is a spring-actuatedmechanism. In another embodiment, at least one actuated mechanism is apneumatic-actuated mechanism. A pressurizing apparatus is used topressurize the pneumatic-actuated mechanism. Various types of actuationconfigurations, such as spring configurations and pneumaticconfigurations or a combination thereof, and sensors may be implementedin or on the insert to provide for control of the actuated mechanism andmeasurement of numerous parameters relating to the balancing of thejoint. Customized graphical user interfaces (GUIs) are provided forreal-time control and visualized feedback of adjustments. Sensor datamay also be collected and compared with expected or preferred data setsto provide adjustment recommendations and achieve better outcomes basedon historical data. Other features and advantages should become apparentfrom the following description of the preferred embodiments, taken inconjunction with the accompanying drawings.

In other embodiments, the device is a femoral balancer that is used tobalance one or more femoral cuts, such as anterior, posterior, anddistal cuts of the femur. The femoral balancer may be used to locatepins for making final balanced cuts to the femur or may include one ormore blade guiding features to make the cuts directly while the femoralbalancer is attached to the femur.

In some embodiments, the device is an insert for balancing a jointduring repair of the joint. The insert includes a first plate, a secondplate, and an actuator there between. The first plate is configured tointerface with a bone structure of a joint. The second plate includes aplate portion, a transition portion, and a mounting portion. The plateportion is spaced apart from the first plate and is configured tointerface with an opposing bone structure of the joint. The transitionportion extends from the plate portion protruding beyond the perimeterof the first plate. The mounting portion extends in a transversedirection relative to the transition portion in the direction of thefirst plate. The actuator is configured to distribute a force to thefirst plate and to the plate portion. In embodiments, the insertincludes a plurality of sensors for determining a spatial relationshipbetween the first plate and the plate portion.

In some embodiments, the first plate is a bottom plate configured tocontact a tibia during repair of the joint, and the second plate is atop plate where the plate portion is configured to contact a femurduring repair of the joint and the mounting portion extends down beyondthe bottom plate. In embodiments, the mounting portion further includesa body, a first leg, a second leg, a first mounting portion, and asecond mounting portion. The body extends downward from the transitionportion. The first leg extends downward from the body. The second legextends downward from the body adjacent to the second leg forming anouter recess there between. The first mounting portion protrudes fromthe first leg. The second mounting portion protrudes from the secondleg. In some embodiments, the first leg extends further than the secondleg.

In other embodiments, the first plate is a top plate configured tocontact a femur during repair of the joint, and the second plate is abottom plate where the plate portion is configured to contact a tibiaduring repair of the joint and the mounting portion extends up beyondthe top plate. In embodiments, the transition portion includes a firsttransition leg extending from the plate portion and a second transitionleg extending from the plate portion. The mounting includes a first leg,a second leg, a first mounting portion, and a second mounting portion.The first leg extends upward from the first transition leg. The secondleg extends upward from second transition leg and is joined to the firstleg at the distal end of the bottom mounting portion. The first mountingportion protrudes from the first leg. The second mounting portionprotrudes from the second leg.

In some embodiments, the actuator is a pneumatic actuator including abellows made of an inflatable material and the bellows is configured toinflate and pneumatically distribute the force to the first plate and tothe plate portion.

In embodiments, the second plate includes a mounting guide. The mountingguide includes a flange protruding from the mounting portion.

In some embodiments, the device is a joint balancing system forbalancing the joint during repair of the joint. The joint balancingsystem includes any of the embodiments of the insert, such as theembodiments described above. The joint balancing system also includes acutting guide and a mounting fastener. The cutting guide includes aguiding slot configured to guide a cut during the repair of the joint.The mounting fastener couples the cutting guide to the mounting portionwith the mounting fastener extending into the flange. In embodiments,the mounting fastener is a guide pin and the insert includes anadjustment device affixed to the mounting portion configured to adjust aplacement of the guide pin.

In embodiments, the joint balancing system includes a first bone anglesensor for affixing to the tibia during repair of the joint and aninsert angle sensor coupled to the insert. In further embodiments, thejoint balancing system further includes a second bone angle sensor foraffixing to the femur during repair of the joint.

In some embodiments, the device is a distal femoral cutting guide. Thedistal femoral cutting guide includes a guide body, a blade guidingfeature, and a guide rod. The guide body includes a bottom portion, atransition portion, and a front portion. In embodiments, the bottomportion includes a plate like shape and an insertion end. The transitionportion extends from the bottom portion in a direction opposite theinsertion end and curves towards a direction that is transverse to thedirection opposite the insertion end. The front portion extends from thetransition portion in the transverse direction. The blade guidingfeature is a slot extending through the guide body and is configured toguide a distal femoral cut during a joint surgery. The guide rod extendsfrom the bottom portion generally in the transverse direction.

In embodiments, the guide rod includes a base adjoining the bottomportion and an end distal to the bottom portion. The guide rod isnarrower at the end than at the base and taps from the base to the end.In embodiments, the guide rod is formed in the shape of theintramedullary canal of the patient's femur. The shape of the guide rodis based off of measurements taken from an image of the joint of thepatient. In embodiments, the guide rod extends in an initial directionthat is less than ninety degrees relative to the plane of the bottomportion and curves towards extending in a direction that is closer toninety degrees than the initial direction relative to the plane of thebottom portion.

In embodiments, the distal femoral cutting guide includes a cuttingguide sensor and a bone angle sensor. The cutting guide sensor isaffixed to the guide body and the bone angle sensor is configured to beaffixed to the patient's femur while the guide rod is located in theintramedullary canal.

In embodiments, the distal femoral cutting guide includes an adjustmentdevice affixed to the guide body. In embodiments, the adjustment deviceis affixed to the transition portion. The adjustment device isconfigured to adjust the position of the femoral cutting guide and toadjust the position of the blade guiding feature.

In embodiments, the front portion includes a top edge that is curved. Insome embodiments, the top edge has an asymmetric curve with the apexshifted toward one side with the one side being higher than the other.In embodiments, the cutting guide sensor is affixed to the front portionadjacent to the apex of the top edge.

In some embodiments, the device is a distal femoral balancer forbalancing the joint during repair of the joint. The distal femoralbalancer includes a first condyle portion and a second condyle portion.The first condyle portion includes a first front portion, a first bottomportion, a first inner surface, and a first pin guide. The first frontportion is configured to be located anterior to a first condyle of thejoint. The first bottom portion extends from the first front portion.The first bottom portion is configured to be located inferior to thefirst condyle. The first inner surface is shaped to match a surface ofthe first condyle. The first pin guide is configured to receive a firstpin and guide the first pin into the first condyle.

The second condyle portion includes a second front portion, a secondbottom portion, a second inner surface, and a second pin guide. Thesecond front portion is configured to be located anterior to a secondcondyle of the joint. The second bottom portion extends from the secondfront portion. The second bottom portion is configured to be locatedinferior to the second condyle. The second inner surface is shaped tomatch a surface of the second condyle. The second pin guide isconfigured to receive a second pin and guide the second pin into thesecond condyle.

In embodiments, the first pin guide includes a first bore extendingthrough the first front portion and a first flange extending from thefirst bore, and the second pin guide includes a second bore extendingthrough the second front portion and a second flange extending from thesecond bore. The first flange and the first bore are aligned, and thesecond flange and the second bore are aligned. In embodiments, the firstflange and the first bore are coaxial, and the second flange and thesecond bore are coaxial.

In embodiments, the first condyle portion includes a first outer surfaceand the second condyle portion includes a second outer surface. Thefirst outer surface and the second outer surface are configured to matchthe outer surface of the first condyle and the second condylerespectively.

In embodiments, the distal femoral balancer includes a balancer actuatorlocated between the first bottom portion and the first condyle and thesecond bottom portion and the second condyle. In some embodiments, thebalancer actuator is adjacent a distal femoral cut. In some embodiments,the balancer actuator includes a plurality of actuators.

In some embodiments, the device is a posterior femoral balancer forbalancing the femur in flexion. The posterior femoral balancer includesa balancer body, a first posterior condyle portion, a second posteriorcondyle portion, a first posterior pin guide, and a second posterior pinguide. The balancer body is configured to be adjacent to the distal endof the femur. The first posterior condyle portion extends from thebalancer body in a direction transverse to the balancer body. The secondposterior condyle portion extends from the balancer body in the samedirection as the first posterior condyle portion. The first posteriorpin guide and the second posterior pin guide each include a flangeextending outward from the balancer body and a bore extending throughthe balancer body. In embodiments, the flange is coaxial to the bore.

In embodiments, the balancer body includes a connection portion, a firstleg, and a second leg. The connection portion joins the first leg andthe second leg distal to the first posterior condyle portion and thesecond posterior condyle portion. The first posterior pin guide islocated on the first leg and the second posterior pin guide is locatedon the second leg. In embodiments, the connection portion, the firstleg, and the second leg form a ‘U’ shape.

In embodiments, the first leg includes a first rounded end distal to thefirst posterior condyle portion and the second leg includes a secondrounded end distal to the second posterior condyle portion. Inembodiments, the second rounded end protrudes further from the secondposterior condyle portion than the first rounded end protrudes from thefirst posterior condyle portion. In embodiments, the first and secondrounds protrude further than the connection portion forming an indentthere between.

In embodiments, the first posterior condyle portion includes a firstinner surface and the second posterior condyle portion includes a secondinner surface. In embodiments, the posterior femoral balancer includes abalancer actuator adjoining the first inner surface and the second innersurface. The balancer actuator locates between the first and secondposterior condyle portions and the condyles of the femur. Inembodiments, the balancer actuator adjoins the posterior femoral cut. Inembodiments, the balancer actuator includes a first actuator adjoiningthe first inner surface and a second actuator adjoining the second innersurface.

In embodiments, the first posterior condyle portion includes a firstouter surface and the second posterior condyle portion includes a secondouter surface. The first and second outer surfaces are shaped toresemble the posterior of a femoral condyle.

In some embodiments, the device is a whole femoral balancer forbalancing the alignment of the entire femoral component simultaneously.The whole femoral balancer includes an anterior portion, a distalportion, a posterior portion, anterior pin guides, and distal pinguides. The anterior portion locates adjacent the anterior of thefemoral component. The anterior portion includes an anterior edge. Theanterior portion extends from the anterior edge in a first directionthen transitions into a second direction that is transverse to the firstdirection. The distal portion extends in the second direction from theanterior portion and locates adjacent the distal end of the femoralcomponent. The posterior portion extends from the distal portion. Theposterior portion transitions from the second direction to a thirddirection that is opposite the first direction and extends in the thirddirection. The posterior portion locates adjacent the posterior of thefemoral component. The anterior pin guides are located at the anteriorportion. The anterior pin guides are configured to guide pins into theanterior of the femoral component. The distal pin guides are located atthe distal portion. The distal pin guides are configured to guide pinsinto the posterior of the femoral component.

In embodiments, the anterior pin guides each include an anterior boreextending through the anterior portion and an anterior flange extendingfrom the anterior portion and aligned with the anterior bore. The distalpin guides each include a distal bore extending through the distalportion and a distal flange extending from the distal portion andaligned with the distal bore. In embodiments, the anterior bore and theanterior flange are coaxial, and the distal bore and the distal flangeare coaxial.

In embodiments, the anterior portion includes an anterior outer surface.The anterior outer surface includes rounds to form the general shape ofthe anterior of the femoral component. The distal portion includes adistal outer surface. The distal outer surface includes rounds to formthe general shape of the distal end of the femoral component. Theposterior portion includes a posterior outer surface that includesrounds to form the general shape of the posterior of the femoralcomponent.

In embodiments, the anterior portion includes an anterior inner surfaceextending in the first direction. The distal portion includes a distalinner surface extending perpendicular to the anterior inner surface. Theposterior portion includes a posterior inner surface extending parallelto the anterior inner surface. In embodiments, the anterior innersurface, the distal inner surface, and the posterior inner surface areflat surfaces. In embodiments, the anterior portion includes an anteriorchamfer surface extending between the anterior inner surface and thedistal inner surface. The posterior portion includes a posterior chamfersurface extending between the distal inner surface and the posteriorinner surface. In embodiments, the anterior chamfer surface extends at aforty-five degree angle relative to the anterior inner surface and thedistal inner surface. The posterior chamfer surface extends at aforty-five degree angle relative to the distal inner surface and theposterior inner surface.

In embodiments, the distal portion includes a first distal leg and asecond distal leg, each following the shape of a condyle of the femoralcomponent. The posterior portion includes a posterior first condyleportion and a posterior second condyle portion. The posterior firstcondyle portion extends from the first distal leg, and the posteriorsecond condyle portion extends from the second distal leg. In someembodiments, the first distal leg and the second distal leg eachextending from the anterior portion. In embodiments, a distal pin guideis located at each of the distal legs.

In some embodiments, the whole femoral balancer includes actuators forbalancing the femoral component. In embodiments, the actuators includean anterior actuator adjoining the anterior inner surface, a distalactuator adjoining the distal inner surface, and a posterior actuatoradjoining the posterior inner surface. In embodiments, the anterioractuator is located between the anterior inner surface and an anteriorcut. The distal actuator is located between the distal inner surface anda distal cut. The posterior actuator is located between the posteriorinner surface and a posterior cut. In embodiments, the anterior actuatorincludes multiple actuators. The distal actuator includes multipleactuators, such as one adjacent each distal leg. The posterior actuatorincludes multiple actuators, such as one adjacent each posterior condyleportion.

In embodiments, the whole femoral balancer includes an anterioradjustment device located at the anterior portion for adjusting theanterior portion relative to the femoral component and a distaladjustment device for adjusting the distal portion and the posteriorportion relative to the femoral component.

In embodiments, the anterior portion includes an end portion and amiddle portion. The middle portion forms the transition between the endportion and the distal portion. The whole femoral balancer includesrelief slots extending inward from the side edges. In embodiments, twoanterior relief slots extend inward between the end portion and themiddle portion and two distal relief slots extend inward between themiddle portion and the distal portion.

In embodiments, the whole femoral balancer includes an anterior sensoraffixed to the anterior portion and a distal sensor affixed to thedistal portion. In some embodiments, the whole femoral balancer alsoincludes a bone angle sensor that affixes to the femur.

Methods for performing cuts to bones and balancing joints is alsodisclosed herein. In embodiments, the method includes inserting theinsert into the joint. In some embodiments, the joint is the knee. Themethod also includes deploying the actuators. In some embodiments,deploying the actuators includes inflating the bellows. The methodfurther includes drilling a hole or holes into the bone. In embodiments,the holes are located in the femur or tibia. In embodiments, the pinguides or mounting guides are used to guide the drill. The method yetfurther includes placing a pin into each hole(s) in the bone. Inembodiments, the pin guides or mounting guides are used to guide thepin(s) into the bone. The method still further includes mounting thecutting guide onto the pins. In embodiments, the cutting guide ismounted adjacent the pin guides or the mounting portion of the insert.The method further includes cutting the bone using the guiding slot toguide the cut. In embodiments, the cut is made parallel to the plateopposite the bone, at a fixed distance from the plate or at apredetermined angle relative to the plate. For example, the cut may bemade parallel to the bottom plate, at a fixed distance from the bottomplate, or at a predetermined angle relative to the bottom plate 150. Inother embodiments the cut may be made parallel to the top plate, at afixed distance from the top plate, or at a predetermined angle relativeto the top plate.

In embodiments, the method also includes adjusting the angle and/orlocation of the pin guides or the mounting guides. In embodiments,adjusting the angle and/or location of the pin guides or the mountingguides includes manually adjusting or actuating the adjustment device.In embodiments, adjusting the angle and or location of the pin guides orthe mounting guides is performed prior to cutting the bone.

A method for performing a femoral cut using the femoral cutting guide500 is also disclosed. In embodiments, the method includes inserting theguide rod into the intramedullary canal of the femur. In embodiments,the guide rod is inserted so that the guide rod is aligned with the longaxis of the femoral shaft. The method also includes cutting the bone ata fixed angle relative to the guide rod.

In embodiments, the method includes affixing a bone angle sensor to thefemur. And measuring the angle between the cutting guide sensor affixedto the femoral cutting guide and the bone angle sensor. In embodiments,the method further includes adjusting the angle and position of theblade guiding feature. In some embodiments, adjusting the angle andposition of the blade guiding feature relative to the femur includesmanually adjusting or actuating the adjustment device until the bladeguide feature is at the predetermined angle for the cut.

In embodiments, the device is a distal femoral balancer used to balancethe joint. In embodiments, the method includes making a distal femoralcut. Any of the cutting methods and tools described herein may be usedto make the cut. In some embodiments, the method includes removing theinsert after making the cut. The method also includes placing the distalfemoral balancer on the distal femoral cut and deploying the distalfemoral balancer to distract the joint. In embodiments, placing thedistal femoral balancer includes locating the distal femoral balancer asshown in the figures and as described herein. The method furtherincludes forming holes into the bone and placing pins into the holes. Insome embodiments, the bone is a femur. In embodiments, the pin guidesare used to make the holes and to place the pins. In embodiments,placing the pins includes locating the pins at a fixed distance and at afixed angle from the bottom portion of the distracted device. Inembodiments, the method includes mounting a cutting block to the pinsand using the guiding slot to make a second cut to the bone.

In some embodiments, the device is a posterior femoral balancer used tobalance the joint. In embodiments, the method includes making aposterior femoral cut. Any of the cutting methods and tools describedherein may be used to make the cut. In some embodiments, the methodincludes removing the insert after making the cut. The method alsoincludes placing the posterior femoral balancer on the posterior femoralcut and deploying the posterior femoral cut to distract the joint. Inembodiments, placing the posterior femoral balancer includes locatingthe posterior balancer as shown in the figures and as described herein.The method further includes forming holes into the bone and placing pinsinto the holes. In embodiments the bone is a femur. The pin guides 740may be used to make the holes and to place the pins. In embodiments,placing the pins includes locating the pins at a fixed distance and at afixed angle from the bottom portion of the distracted device. Inembodiments, the method also includes mounting a cutting block to thepins and using the guiding slot to make a second cut to the bone.

In some embodiments the device is a whole femoral balancer used tobalance the joint. In embodiments, the method includes placing the wholefemoral balancer over the femoral component. In embodiments, placing thewhole femoral balancer includes locating the whole femoral balancer asshown in the figures and described herein. The method also includescutting the bone. In embodiments, cutting the bone includes performinganterior, distal and/or posterior cuts to the femoral component. Thecuts may be made before or after placing the whole femoral balancer overthe femoral component. The method also includes deploying the wholefemoral balancer to distract the joint.

The method may also include forming holes into the bone and placing pinsinto the holes. In embodiments, the bone is a femur. In embodiments, thepin guides are used to make the holes and to place the pins. One or moresets of holes are formed and one or more sets of pins are placed in theholes. In embodiments, placing the pins includes locating the pins at afixed distance and at a fixed angle from a predetermined portion of thedistracted device. The method may also include mounting a cutting blockto the pins or to one set of pins and using the guiding slot to make acut to the bone. In embodiments, the method includes mounting a secondcutting block to another set of pins and making another cut to the bone.

In some embodiments, the method includes adjusting the relative angleand position of all or a portion of the whole femoral balancer, such asthe anterior portion or the distal portion. In embodiments, adjustingthe relative angle and position of all or a portion of the whole femoralbalancer may include manually adjusting or actuating the anterioradjustment device and/or the distal adjustment device. In someembodiments, the method also includes measuring the angle of all or aportion of the whole femoral balancer relative to the bone, such as thefemur 8. In embodiments, measuring the angle of all or a portion of thewhole femoral balancer relative to the bone may include measuring therelative angle between the anterior sensor and the bone sensor andmeasuring the relative angle between the distal sensor and the bonesensor. Other sensors, such as a sensor located on the posterior portionmay also be used. In embodiments, the method includes affixing a bonesensor to the bone. The step of adjusting the relative angle andposition of the whole femoral balancer may be performed prior to makingthe cuts.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments disclosed herein are described in detail withreference to the following figures. The drawings are provided forpurposes of illustration only and merely depict typical or exemplaryembodiments. These drawings are provided to facilitate the reader'sunderstanding and shall not be considered limiting of the breadth,scope, or applicability of the embodiments. It should be noted that forclarity and ease of illustration these drawings are not necessarily madeto scale.

FIG. 1 is a functional block diagram of a joint balancing system,according to one embodiment of the invention.

FIG. 2 is an illustration of an embodiment of the insert of FIG. 1disposed in a knee joint.

FIG. 3 is a perspective view illustration of an embodiment of the insertof FIG. 1 with displacement sensors.

FIG. 4 is an illustration of a perspective view of an embodiment of theinsert of FIG. 1 with a pneumatic actuator.

FIG. 5 is an illustration of an exploded view of the insert of FIG. 4.

FIG. 6 is an illustration of a perspective view of the pneumaticactuator of FIGS. 4 and 5.

FIG. 7 is a top view of a bellows 182 of FIG. 6.

FIG. 8 is an illustration of a perspective view of the electronics boardof FIGS. 4 and 5.

FIG. 9 is an exploded view illustration of an embodiment of the insertof FIG. 1 with a plurality of spring actuators.

FIG. 10 is an alternate exploded view illustration of the insert of FIG.9 without the actuators.

FIG. 11 is a perspective view illustration of an embodiment of theinsert of FIG. 1 with a unicompartmental configuration.

FIG. 12 is an illustration of a perspective view of an embodiment of thecontroller assembly of FIG. 1 connected to an insert.

FIG. 13 is an illustration of a perspective view of the controller ofthe controller assembly of FIG. 12.

FIG. 14 is an illustration of an exploded view of the controller of FIG.13.

FIGS. 15 and 16 illustrate an embodiment of a cutting guide assemblyconnected to the insert that is used to guide cutting bone and tissueduring balancing of the joint.

FIGS. 17-20 illustrate an embodiment of an insert with an integratedmount for a tibial cutting block.

FIGS. 21-24 illustrate an alternate embodiment of the insert 100 ofFIGS. 17-20.

FIGS. 25-28 illustrate an embodiment of an insert with an integratedmount for a femoral cutting block.

FIGS. 29-32 illustrate an alternate embodiment of the insert of FIGS.25-28.

FIGS. 33-40 illustrate an alternate embodiment of the insert of FIGS.25-32.

FIGS. 41-48 illustrate an embodiment of a femoral cutting guide.

FIGS. 49-52 illustrate an embodiment of the femoral cutting guide ofFIGS. 41-48 after the distal femoral cut is made.

FIGS. 53-60 illustrate an embodiment of a distal femoral balancer.

FIGS. 61-68 illustrate an embodiment of a posterior femoral balancer.

FIGS. 69-76 illustrate an embodiment of a whole femoral balancer.

FIGS. 77-80 illustrate an alternate embodiment of the whole femoralbalancer of FIGS. 69-76.

The various embodiments mentioned above are described in further detailwith reference to the aforementioned figured and the following detaileddescription of exemplary embodiments.

DETAILED DESCRIPTION

Disclosed herein are systems, devices, and methods for balancing a jointduring surgical procedures on joints, such as prosthetic arthroplasty.FIG. 1 is a functional block diagram of a joint balancing system 50,according to one embodiment of the invention. Joint balancing system 50may include a trial insert (“insert”) 100, a controller assembly 200,and a display system 300. The joint balancing system 50 includes aninsert 100 with one or more plates, one or more sensors and at least oneactuator/actuated mechanism for actuating the device against one or moreparts of the joint as illustrated in FIGS. 2-11. The actuated mechanismmay be fluid powered, such as by air, electromechanical,electromagnetic, mechanical, piezoelectric, or a combination thereof.Other actuated mechanisms may also be used. The one or more plates aredisposed between bone structures which define the joint, such as thefemur and the tibia in a knee joint. The one or more sensors may provideforce, position and angular data about the movement of the joint, which,along with the applied force data from the actuation mechanism, providefor highly accurate and dynamic adjustments of the joint. Variousconfigurations of the actuators and sensors may be implemented in or onthe insert 100 to provide for control of the insert 100 and measurementof numerous parameters relating to the balancing of the joint. Theaddition of an actuated mechanism to the inserts provides numerousbenefits to the process of balancing a joint during surgical procedures,such as arthroplasty. The surgeon is able to apply a known andcontrolled amount of force to the joint and correlate the measured load,movement and angular data with the applied force to more preciselydetermine if adjustments should be made. The actuated mechanism may alsobe capable of dynamic actuation from a variety of different actuationpoints on the insert, providing the ability to apply different loadamounts, different amounts of movement and different angles of movementto more accurately simulate the movement of the joint and measure theresults. The load can be measured across any range of motion to providesignificant improvements in load balancing.

The insert 100 may include an electronics board 140. The electronicsboard 140 may include a board module 141 and a board communicationmodule 143. The board module 141 may be configured to obtain the datafrom the sensors and send the data to the controller assembly 200 viathe board communication module 143. The board module 141 may also beconfigured to relay a signal from the controller assembly 200 to theactuators. The board module 141 may also be configured with a safetyoverride to control the actuator force or the magnitude of distractionor displacement. The board module 141 may further be configured tocommunicate a signal when the insert 100 is unbalanced and communicateanother signal when the insert is balanced. The signal may cause analert, such as an auditory alert or a visual alert provided byelectronic hardware attached to the electronics board 140 and/or fromthe display system. The auditory alert may be provided by a soundsource, such as a speaker or a piezoelectric sound generator. The visualalert may be provided by a light source, such as a light emitting diode.The board module 141 may yet further be configured to provide guidancefor alignment during surgery to surgical instruments, such as drills andsaws. The communications module 143 may be configured to send/receiveelectronic signals to/from the controller assembly over a wired orwireless connection. In some embodiments, the communications module 143is configured to communicate with other surgical instruments such asdrills and saws.

The controller assembly 200 may be used to manually or remotely controlthe actuators within the insert 100. In some embodiments, the controllerassembly 200 physically or mechanically controls the actuators which mayallow for manual manipulation of the movement of the actuators by asurgeon or medical technician. In other embodiments, the controllerassembly 200 electronically controls the actuators which can bemonitored and programmed as a computing device with a processor andmemory.

Controller assembly 200 may include a controller 240. Controller 240 mayinclude a controller communication module 259. The controllercommunication module 259 is configured to send/receive signals from theinsert 100 and from the display system 300 over a wired and/or awireless connection. In some embodiments, the controller communicationmodule 259 is configured to communicate with other surgical instruments,such as drills and saws. The controller communication module 259 mayrelay the guidance provided by the board module 141 to the surgicalinstruments.

Controller assembly 200 may be manipulated through one or more inputdevices, such as a mouse, a keyboard, capacitive buttons, or aninteractive display. The interactive display may be part of the displaysystem 300 and may display the controls for each actuator along with therelevant values and other measured parameters for easy comparison duringjoint balancing. A single controller 240 may be configured to apply thesame pressure to all of the actuators. This may simplify the design andensure that an equal force/pressure is applied at each actuator.

Display system 300 may be a computing device with a processor andmemory, such as a computer, tablet, smartphone, or other electronicdevice that may be used to display the GUI. Display system 300 mayinclude a display communication module 310, a display module 320, and adisplay 330, such as a monitor. Display communication module 310 isconfigured to send/receive wired or wireless communications to/from thecontroller assembly 200.

Display module 320 may provide customized graphical user interfaces(GUIs) for viewing on display 330. The GUIs may display relevant datafor real-time control and visualized feedback of adjustments throughvisual alignment guides that indicate when all of the measuredparameters are within preferred ranges. The GUIs may also present thevalues for the parameters measured by the various sensors.

Sensor data may also be collected and compared with expected orpreferred data sets to provide adjustment recommendations and achievebetter outcomes based on historical data. A GUI may provide visual oraudio indications as to whether the joint is balanced by comparing themeasured parameters with known accepted ranges of the values. Inembodiments, the GUI may provide the force applied to the top plate 110and the bottom plate 150. The force may be determined using the heightand pressure measurements provided by the sensors. The force may bedetermined by the display system 300, such as by the display module 320,or by another system/module.

Joint balancing system may also include a data store 90. The data store90 may be a separate system connected to either the display system 300or the controller assembly 200, or may be located within either thedisplay system 300 or the controller assembly 200. In embodiments, thedata in the data store 90 may be uploaded to a central server foranalysis.

In one embodiment, a visual alignment guide may be presented whichgraphically illustrates the alignment of the two plates and the movementof the actuators within the joint in real-time. The visual alignmentguide may provide guide lines or circular targets that will help thesurgeon achieve a desired alignment. The alignment guide may alsoprovide color-coded visual graphics to indicate whether an alignment isgood (green) or bad (red).

In some embodiments, the GUI displays one or more diagrams related tothe positioning of the insert 100. The diagrams may display the relativedisplacement between the top and bottom plates in one or more of thesensor locations. The GUI may also display the tilt between the top andbottom plates. The GUI may include multiple graphs. One graph maydisplay the history of the tilt in the mediolateral (side to side)direction. Another graph may display the tilt in the anteroposteriordirection. The GUI may also display the knee flexion angle, pressure,force, and battery voltage. The GUI may also provide buttons to save thedata or to generate a screen capture for future reference. This data andinformation may be archived in the data store 90. A third graph maydisplay the history of the distance between the top and bottom plates.The GUI may also display previously recorded data against which the realtime data can be compared.

In some embodiments, the GUI displays three diagrams. One diagramdisplays the data collected while the knee is at 0 flexion, anotherdiagram displays the data collected while the knee is at 90 degreesflexion, and the third diagram displays the data in real time.

In some embodiments, the GUI can be used prior to surgery to set up acustom or patient-specific balance that is unique to the patent and/orthe insert 100. The GUI can also contain a list of instructions as towhere the problem is within the joint and can provide a recommendationto the surgeon on how to correct the problem. The GUI can also displayinformation from other devices or instruments, such as computernavigation systems, surgical robots, instruments, such as drills andsaws, tourniquet sensors, etc.

FIG. 2 is an illustration of an embodiment of the insert 100 of FIG. 1disposed in a knee joint. In the embodiment illustrated, the insert 100includes a top plate 110 and a bottom plate 150 separated by actuators180 positioned at various points on the interior surfaces of the topplate 110 and bottom plate 150. The top plate 110 is disposed against afemur 8, while the bottom plate 150 is disposed against a tibia 10. Theinsert 100 is additionally configured with one or more sensors (shown inFIG. 3) disposed along the top plate 110 and/or the bottom plates 150.The sensors are configured to measure and determine various parametersrelated to the balancing of the joint, as described herein.

The insert 100 may be designed as a temporary insert that is positionedinto the joint only during a joint balancing procedure, such that it isreplaced by a permanent insert of similar shape and size once the jointbalancing is complete. In another embodiment, the insert 100 may bepermanent, such that it will remain in position between the adjacentbones once the joint has been balanced.

The insert 100 may be a standalone device before insertion into thejoint. The top plate 110 and bottom plate 150 may vary in shape and sizeand be aligned in parallel planes. The general shape of the top plate110 and corresponding bottom plate 150 (is designed to fit within theknee joint and provide a large surface area to interface with, such ascontacting, the bony surfaces of the adjacent femur 8 and tibia 10. Inthe embodiment illustrated, insert 100 includes four total actuators 180(three visible) disposed between the top plate 110 and the bottom plate150. The actuators 180 may be evenly spaced and positioned withindifferent quadrants of the insert 100 to provide for actuation fromdifferent points within the insert that will allow for dynamic loadbalancing at each actuator and different angles of actuation of theinsert 100. For example, if two adjacent actuators 180 are actuated, theinsert may be disposed at an angle which slopes from one side of theinsert 100 to the other. The number of actuators 180 may vary and may beas few as one. The actuators 180 may be placed in other configurations,such as triangular, circular, or irregular placements. The actuators mayalso be tilted or angled to generate shear or rotational forces(torque).

A method of balancing a joint using the insert 100 in accordance withone embodiment of the invention will now be described. The balance ofthe joint may be measured at several stages of the surgical procedure.For example: measurements may be taken before making any bone cuts, orafter making the tibial bone cut against the uncut femoral surface, orafter making the femoral cut against the cut femoral surfaces or againsta trial femoral prosthesis, or with trial femoral or tibial prosthesesin place, or with the final femoral and tibial prostheses in place.During a first step, the insert is positioned in a gap or opening of ajoint between two opposing bone structures, such as an opening between afemur 8 and a tibia 10 in a knee joint. In some embodiments,insertion/extraction tools are used to insert the insert 100 into theopening. Next, one or more of the actuators 180 is activated to apply aload to the bone structures of the femur 8 and tibia 10. The sensorsmeasure one or more parameters relating to the joint, such as themovement, pressure, angle, position, range of motion, gap, load appliedby each actuator, etc. The measurements may provide an indication as towhether the joint is balanced—i.e. whether pressure is being evenlyapplied to the insert by the opposing bone structures, whether the jointis able to move within a desired range of motion, the magnitude of thegap between the surfaces of the femur 8 and tibia 10 and the change ingap when the knee is flexed or extended, whether the ligamentssurrounding the joint are under too much tension, etc. The measurementsmay also indicate that the bone cuts are not optimum, for example, thetibia 10 may have been cut in too much varus or valgus, the femur 8 mayhave been cut in too much varus or valgus, or in external or internalrotation, or the distal cut of the femur may have been made too deepresulting in a mismatch of the gap between the surfaces of the femur andtibia at different flexion angles. If the measurements and analysis ofthe measurements indicates that the joint is not properly balanced orthe bone cuts are not appropriate, the surgeon will make one or moreadjustments to some portion of the joint to improve the balance of thejoint. The adjustments may include: re-cutting the bones, releasing ortightening ligaments, adjusting the placement or rotation of theprosthetics or the insert 100; cutting away portions of the bones,ligaments or cartilage; or increasing or decreasing the height of theinsert 100 to better fit the gap in the joint. The joint may be testedagain by actuating one or more of the actuators and measuring theparameters to determine if improvements have been made. This process maybe repeated till the surgeon is satisfied with the measurements. Inembodiments including a fluid powered actuator, measuring thedistraction while changing the pressure of the fluid powered actuatormay be used to characterize the biomechanical properties of the softtissues and aid in selecting the optimal balance.

At the point where the measurements fall within certain acceptableranges, the joint is considered to be balanced. If the insert 100 isdesigned to function as a permanent prosthetic, it is left in place inthe joint opening. If the insert 100 is configured only as a measurementand testing tool, it is removed and then replaced with a permanentprosthesis of identical dimensions. In some embodiments, the datacollected by the sensor(s) are used to generate a custom implant ondemand.

Further details of the properties and function of the insert 100 will bedescribed below with regard to the actuators, sensors, shape andconfiguration of the device, controllers and user interface andadditional tools for joint balancing.

Sensors

Sensors disposed on or within the insert 100 can be configured tomeasure and be used to determine numerous different parameters relatedto the balancing of the joint. For example, the sensors can beconfigured to measure and be used to determine the force, or load, beingapplied by the actuators and the resulting pressure received on varioussections of the top or bottom plates by the adjacent bone. Examples ofthese sensors are load cells, strain gages, pressure sensors, etc. Forspring actuators, the spring force may be calculated indirectly, forexample using the known spring stiffness and the measured spring lengthusing displacement sensors. Sensors can also be configured to monitordistance of movement, either total movement between the top and bottomplates or movement of each individual actuator. Examples of thesesensors are magnetic sensors, optoelectric sensors, and monitoring thestroke of the actuator mechanism (e.g. screw driven actuators). Sensorsmay also measure angles of motion, and even angular positions throughthe use of accelerometers, magnetometer, and gyroscopes.

The inserts 100 may incorporate a plurality of different sensors inorder to measure different types of parameters or to measure the sametypes of parameters at different places on the insert 100. The sensorscommunicate via a wired or wireless connection, and may be powered by anexternal power source or an internal power source within each sensor ora power source located within the insert 100.

FIG. 3 is a perspective view illustration of an embodiment of the insert100 of FIG. 1 with sensors 102. The actuators 180 are not shown forclarity. Sensors 102 may be used to determine the relationship betweenthe top plate 110 and the bottom plate 150, such as the spatialrelationship, including the distance and angle between the top plate 110and bottom plate 150, and the pressure between the top plate 110 and thebottom plate 150. In the embodiment illustrated, sensors 102 aredisplacement sensors with corresponding magnets 104. The sensors 102 andmagnets 104 may be located on opposite interior surfaces of the topplate 110 and the bottom plate 150. Insert 100 may include any numberand configuration of sensors 102 and magnets 104. In the embodimentillustrated, the insert 100 has four sensors 102 on an interior surfaceof the bottom plate 150 and four corresponding magnets 104 configured onan interior surface of the top plate 110 for holding the two platestogether. The sensors 118 measure displacement between the top plate 110and bottom plate 150 at multiple locations and calculate tilt in twodirections. The sensors 102 may be Hall Effect sensors. The sensors 102and magnets 104 may be aligned between the top plate 110 and the bottomplate 150.

In some embodiments, a single sensor 102 is positioned in a center areaof the insert 100, such that the top plate 110 and bottom plate 150pivot around the sensor 102 and the corresponding magnet 104. The singlesensor 102 is therefore able to measure displacement between the topplate 110 and the bottom plate 150, as well as rotational movement inthree directions. In one embodiment, the single sensor 102 is a threedimensional magnetometer.

In some embodiments, the sensor 102 is a pressure sensor. In theseembodiments, the sensor 102 may cover a substantial portion of a surfaceof the top plate 110 or bottom plate 150 and may adjoin that surface. Inthese embodiments, the pressure sensors may be configured such that apressure map can be determined and provided by the GUI including therelative position of femoral condyles during the balancing of a knee. Inone embodiment, the sensor is positioned above a substantial portion ofan interior surface of the bottom plate 150. In another embodiment, thesensor 102 is positioned on an exterior surface of the bottom plate 150.In yet another embodiment, the sensor 102 is positioned on an interiorsurface of the top plate 110. In a further embodiment, the sensor 102 ispositioned on the articular exterior surface of the top plate 110. Thesensor 102 is capable of measuring pressure distribution over the entiresurface area of the adjoining surface and may be configured to measurecontact pressure between the femur 8 and tibia 10.

Additionally, one or more of the sensors 102 may be angle measurementsensors (including accelerometers, magnetometers and gyroscopes) thatare configured to measure the angle of the insert relative to the leg,thigh, or any other part of the body, as well as relative to the ground.This information can be used to determine whether there is an imbalancein the joint and to assess if the imbalance is due to ligament imbalanceor improper bone cuts.

Pneumatic-Actuated Mechanisms

In some embodiments, the insert 100 may be actuated by fluid power, suchas by pneumatics or hydraulics. Fluids such as air, saline, or moreviscous fluids, such as gels, may be used to as the actuating fluid.FIGS. 4-7 illustrate an embodiment of the insert 100, where the insert100 is a pneumatic insert. FIG. 4 is an illustration of a perspectiveview of an embodiment of the insert of FIG. 1 with a pneumatic actuator180.

In the embodiment illustrated, top plate 110 includes a plate portion120 and an articular portion 130. The articular portion 130 attaches toplate portion 120 and is configured to interface with, such as by director indirect contact, the natural or artificial femur. The top plate 110or bottom plate 150 may include one or more grooves 138. The grooves maybe oval shaped to match the natural shape of the condyles of theadjacent bone. In the embodiment illustrated, grooves 138 are located onthe outer surface of the top plate 110 with a groove 138 on each side ofthe top plate 110 which would receive corresponding condyles 14 (seeFIG. 2) of the femur 8.

The grooves 138 may include an articular contact surface 139 thatarticulates with the articular surface of the natural or artificialfemur. In the embodiment illustrated, the grooves 138 and articularcontact surface 139 are located on an outer surface of the articularportion 130, located opposite both the top portion 120 and the bottomplate 150. The articular portion 130, including the grooves 138 and thearticular contact surfaces 139, can be shaped to accommodate any femoralarticular size or shape.

FIG. 5 is an illustration of an exploded view of the insert 100 of FIG.4. The actuator 180 is located between the top plate 110 and the bottomplate 150. The top plate 110 and the bottom plate 150 may be combined toor may individually match the natural shape of the tibial bone or matchthe shape of an implant, such as a tibial tray. A pneumatic actuator 180may be formed of one or more bellows. The actuator may include multipleconfigurations of bellows, such as first bellows 181 and second bellows182. In the embodiment illustrated, the actuator 180 includes fourlayers of bellows with one first bellows 181 and three second bellows182. In embodiments, the first bellows 181 and the second bellows 182are stacked between the top plate 110 and the bottom plate 150. Theactuator 180 is connected and fluidly coupled to a fluid supply line 70.The fluid supply line 70 allows the fluid, such as air, to be added orremoved from the one or more bellows to position the top plate 110relative to the bottom plate 150.

Plate portion 120 may include a plate body 121, a board receivingfeature 124, a connection feature 128, and a connection hole 129. Platebody 121 may include a plate body connection end 122, a plate bodyinsertion end 123, a plate body first side 124, and a plate body secondside 125. Plate body connection end 122 may generally have a convexshape. The curvature of the convex shape may be similar to the curvatureof the flatter portion of an ellipse. Plate body insertion end 123 isopposite plate body connection end 122. Plate body insertion end 123 mayinclude a concave portion and may generally have the shape of a portionof a Cassini oval that is between an oval and a lemniscate. Plate bodyfirst side 124 and plate body second side 125 may be symmetrical and mayeach have a circular shape. Plate body connection end 122, plate bodyinsertion end 123, plate body first side 124, and plate body second side125 may form the perimeter of plate portion 120.

Board receiving feature 126 may protrude from plate body 121 towardsarticular portion 130 and away from bottom plate 150. Board receivingfeature 126 may generally include a T-shape. Board receiving feature 126may also include a cavity for receiving electronics board 140. Boardreceiving feature 126 may further include one or more electronicsreceiving features 127. The electronics receiving features 127 may be aprotrusion or a recess configured to receive electronic hardware 142coupled to electronics board 140.

Connection feature 128 may extend from plate portion 120 at plate bodyconnection end 122 generally towards bottom plate 150. Connectionfeature 128 may extend in the opposite direction relative to boardreceiving feature 124. Connection hole 129 may extend through connectionfeature 128 to provide access to electronics board 140.

Articular portion 130 may include an articular portion body 131, arecess 137, and a connection end bevel 136 along with the grooves 138and the articular surfaces 138. Articular portion body 131 may generallyinclude the same shape about its perimeter as plate body 121. Articularportion body 131 may include an articular portion body connection end132, an articular portion body insertion end 133, an articular portionbody first side 134, and an articular portion body second side 135.Articular portion body connection end 132 may generally have a convexshape. The curvature of the convex shape may be similar to the curvatureof the flatter portion of an ellipse. Articular portion body insertionend 133 is opposite articular portion body connection end 132. Articularportion body insertion end 133 may include a concave portion and maygenerally have the shape of a portion of a Cassini oval that is betweenan oval and a lemniscate. Articular portion body first side 134 andarticular portion body second side 135 may be symmetrical and may eachhave a circular shape. Articular portion body connection end 132,articular portion body insertion end 133, articular portion body firstside 134, and articular portion body second side 135 may form theperimeter of articular portion 130.

Recess 137 may be located opposite grooves 138 and articular surfaces139. Recess 137 may include a T-shape and may be configured to receiveboard receiving feature 126. Connection end bevel 136 may be located atconnection end 132 and may be centered in connection end 132 between togrooves 138.

The insert 100 may include attachment mechanisms 112. Attachmentmechanisms 112 may be fasteners, such as detent posts. The articularportion 130 may be attached to the top portion 120 using the attachmentmechanisms 112. Screws 113 may extend through and up from boardreceiving feature 126. Attachment mechanisms 112 may be configured tocouple to screws 113 to hold plate portion 120 to articular portion 130.

The bottom plate 150 may include a bottom plate body 151, one or moremagnet recesses 156, a connector recess 157, and restraining holes 158.The bottom plate body 151 may generally include the same shape about itsperimeter as plate portion body 121 and articular body portion 131.

Bottom plate body 151 may include bottom plate body connection end 152,a bottom plate body insertion end 153, a bottom plate body first side154, and a bottom plate body second side 155. Bottom plate bodyconnection end 152 may generally have a convex shape. The curvature ofthe convex shape may be similar to the curvature of the flatter portionof an ellipse. Bottom plate body insertion end 153 is opposite bottomplate body connection end 152. Bottom plate body insertion end 153 mayinclude a concave portion and may generally have the shape of a portionof a Cassini oval that is between an oval and a lemniscate. Bottom platebody first side 154 and bottom plate body second side 155 may besymmetrical and may each have a circular shape. Bottom plate bodyconnection end 152, bottom plate body insertion end 153, bottom platebody first side 154, and bottom plate body second side 155 may form theperimeter of bottom plate body 151.

Each magnet recess 156 may extend into bottom plate body 151 from aninterior surface of bottom plate body 151 and may be configured to holdone or more magnet 104. In the embodiment illustrated, insert 100includes one magnet in each magnet recess 156. Each magnet recess 156may be adjacent actuator 180. The embodiment illustrated includes threemagnet recesses 156 arranged in a triangular pattern. In otherembodiments, different numbers of magnetic recesses 156 and magnets 104are used and arranged in different patterns. Each magnet recess 156 andthe magnet 104 therein may be aligned with a sensor 102.

Connector recess 157 may extend into bottom plate body 151 from bottomplate body connection end 152. In the embodiment illustrated, connectorrecess 157 is a cuboid shaped recess. Connector recess 157 is configuredso that bottom plate 150 does not interfere with connector feature 128when actuator 180 is in its narrowest configuration, such as when thebellows 182 are empty.

Restraining holes 158 may be used to secure bottom plate 150 to topplate 110. The insert 100 may include a restraining device 115. Therestraining device 115 is configured to hold the top plate 110 and thebottom plate 150 together. The restraining device 115 is also configuredto prevent the top plate 110 and the bottom plate 150 from separatingbeyond a desired distance and is configured to allow the actuator 180 toexpand up to a predetermined amount. In the embodiment illustrated, thepredetermined amount of expansion is 6 millimeters, which may allow theinsert 100 to expand from eight millimeters to fourteen millimeters. Inthe embodiment illustrated, the restraining device 115 is made ofmedical suture material. In other embodiments, the restraining device115 is integral to each chamber of the pneumatic actuator 180. In otherembodiments, the restraining device 115 is a skirt around the perimeterextending between the top plate 110 and the bottom plate 150. Someembodiments may be configured to expand beyond fourteen millimeters.Other embodiments are configured shims are added to the bottom plate 150to increase the distraction. In yet other embodiments, an articularportion 130 with an increased thickness is attached to the top plate 110to further expand the height of the insert 100 beyond fourteenmillimeters.

In the embodiment illustrated, the insert 100 includes two restrainingdevices 115, one on each side of the insert 100. The restraining device115 may contact the outer surface of the bottom plate 150, pass throughthe restraining holes 152 and be affixed to the top plate 110. In theembodiment illustrated, each restraining device 115 is affixed to thetop portion 120 with retaining fasteners 124, such as screws.

The insert 100 may also include an electronics board 140. Theelectronics board 140 may be housed within the top plate 110 or thebottom plate 150. In the embodiment illustrated, the electronics board140 is located within board receiving feature 126 and is adjacentactuator 180. An electronics connector 60 may be electronically coupledto the electronics board 140 and may extend from the electronics board140, through connector hole 129, and to the controller assembly 200. Theelectronics connector 60 may be an electric wire with an outer casing.Electronic hardware 142 may be coupled to and adjacent the electronicsboard 140. The electronic hardware 142 may include sensors, soundsources, such as speakers and piezoelectric sound generators, and lightsources, such as light emitting diodes.

FIG. 6 is an illustration of a perspective view of the pneumaticactuator 180 of FIGS. 4 and 5. FIG. 7 is a top view of the first bellows181 of FIGS. 5 and 6. Referring to FIGS. 6 and 7, each bellows is madeof an inflatable material that includes one or more pneumaticcompartments 187 surrounded by a compartment boundary 188. The bellowsand the various compartments 187 are manifolded together. In theembodiment illustrated, the bellows have manifolds between compartments187 of adjacent bellows as described herein. In other embodiments, amanifold can be used to plumb each bellows separately. In otherembodiments, each bellows is plumbed to a separate fluid source andactuated separately. The pneumatic compartments are configured toinflate such that the pneumatic compartments expand and distribute thepneumatic force over different regions of the top plate 110 and bottomplate 150. The shape, size, and number of layers of the bellows 182within the actuator 180 may be selected based on the desired force at agiven pressure. In embodiments, the nominal force is 20 lbf. In someembodiments, the force should not vary by more than 15%. In someembodiments, the force should not vary by more than 3 lbf.

The shape of the bellows 182 may also be configured to maximize thetransmission of forces as well as the magnitude of distraction. Changingthe shape of the bellows 182 may change the surface area which maychange the magnitude of the force (for the same pressure). Changing theshape of the bellows 182 can also affect the location of the center ofapplication of the force.

In the embodiment illustrated, the first bellows 181 and the secondbellows 182 have the same general dog bone shape. The first bellows 181has four compartments 187 with each compartment 187 in one quadrant ofthe first bellows 181. Each compartment 187 is a quarter of the dog boneshape. In the first bellows 181 the four compartments 187 are in directfluid communication. The compartment boundary 188 for each compartmentis open to the other compartments 187 along the neck of the dog boneshape. The first bellows 181 may include a fluid communication hole 184through the top of each compartment 187, on the bottom of eachcompartment 187, or through both.

The first bellows 181 also has a fluid connection tab 189 and a fluidsupply connector 183. The fluid connection tab 189 may extend out fromthe neck of the dog bone shape and be in fluid communication with thefluid supply connector 183. The fluid supply connector 183 is configuredto fluidly connect the first bellows 181 to the fluid supply line 70.

The second bellows 182 has four compartments 187 with each compartment187 in one quadrant of the second bellows 182. Each compartment 187 is aquarter of the dog bone shape. In the second bellows 182 the fourcompartments 187 are not in direct fluid communication. The compartmentboundary 188 for each compartment completely encloses the compartmentoff from the other compartments 187. The second bellows 182 may includea fluid communication hole 184 through the top of each compartment 187,on the bottom of each compartment 187, or through both.

The actuator 180 may include multiple annular seals 186 and multipleseals 185. In the embodiment illustrated, annular seals 186 are adhesiverings and seals 185 are adhesive disks. In other embodiment, annularseals 186 and seals 185 are formed by bonding the bellows to theadjacent structure, such as an adjacent bellows, a top plate 110, or abottom plate 150. In some embodiments, the annular seals 186 and seals185 are formed using RF welding. An annular seal 186 may be locatedbetween adjacent compartments 187 of adjacent bellows, such as the firstbellows 181 and a second bellows 182 or two adjacent bellows 182. Theannular seal 186 seals the adjacent compartments 187 around the adjacentfluid communication holes 184 so that the adjacent compartments 187 aremanifolded together in fluid communication. In embodiments, the annularseals 186 and manifold formed by thereby can withstand a vacuum. Theseals 185 are located at the outer surface of a compartment 187 that isnot adjacent to another compartment 187. The seals 185 may be configuredto seal a fluid communication hole 184 and may attach the first bellows181 or the second bellows 182 to either the top plate 110 or the bottomplate 150.

FIG. 8 is an illustration of a perspective view of the electronics boardof FIGS. 4 and 5. The electronics board 140 may include a board surface731 that faces the bottom plate 150 with the actuator 180 there between(as shown in FIGS. 5 and 6). One or more sensors 102 may be connected tothe electronics board 140. The location and number of sensors 102 maycorrespond to the number and placement of the one or more magnets 104located at the bottom plate 150 (shown in FIG. 7B). The sensors 102 maydetect the distance from the magnets 104, which may allow the distanceand the angle between the top plate 110 and the bottom plate 150 to bedetermined.

Spring-Actuated Mechanisms

In some embodiments, the insert 100 is configured with one or moremechanical actuators 180, such as constant or variable force springs,which apply a load to the plates and the adjoining bone structures ofthe joint. The number and type of actuators 180 may vary depending onnumerous factors, including the intended function of the device and theamount of control needed over the actuation process.

FIG. 9 is an exploded view illustration of an embodiment of the insertof FIG. 1 with a plurality of spring actuators. Referring to FIG. 9, theactuators 180 are springs. The actuators 180 are not permanentlyattached with the top plate 110 and bottom plate 150 and can thereforebe easily removed in order to exchange them with different actuatorsthat have a different stiffness. In addition, the unattached actuators180 also allow for the exchange of the top plate 110 and/or bottom plate150 with plates of different size, shape and thickness in order to bestmatch the needed dimensions of the area where the insert 100 is beingpositioned. The unattached actuators 180 may then be secured within theinsert 100 by providing top actuator recesses 111 in top plate 110 andbottom actuator recesses 161 in bottom plate 150. The top plate 110 andbottom plate 150 may also be connected with each other by a flexible orelastic tether that holds the entire insert assembly together.

Alternatively, the actuators 180 may be attached (either permanently orremovably) with the top plate 110 or bottom plate 150 (or both) by oneor more attachment mechanisms. In one example, the ends of the actuators180 may be bonded to the top plate 110 and the bottom plate 150 withvarious glues such as cyanoacrylate or potted in plate with epoxy,polyurethane, etc. The actuators 180 could also be manufactured withcustomized ends which snap into a corresponding retaining mechanism onthe respective top plate 110 and bottom plate 150 and lock the ends ofthe actuators 180 into place. The actuators 180 could also bemanufactured and formed within one or both of the top plate 110 andbottom plate 150.

The shape and dimensions of the spring-actuated mechanism may also varyconsiderably, but in the embodiments described and illustrated herein,the actuators 180 are springs which are cylindrically-shaped with adiameter of approximately 4-8 millimeters (mm) and an expandable heightof approximately 6-10 mm. The actuators 180 may be configured to apply aforce in the range of 1-50 pounds per actuator, have a force accuracy ofapproximately 1 percent and a displacement accuracy of approximately 0.2mm. When a plurality of actuators 180 are used, each actuator 180 may beindependently controlled and expanded or contracted in order to obtainan angled, or tilted top plate 110 or bottom plate 150, as has beenpreviously described. The number of actuators 180 used may vary betweenone to four or more, and may depend on the size of the actuator 180 andsurface areas of the top plate 110 and the bottom plate 150 on whichthey are disposed. The actuators 180 may have varying stroke lengths,shapes, dimensions and force capacities.

In one embodiment, actuators 180 are helical or coil springs thatgenerate force when compressed. In another embodiment, actuators 180 areconical or volute springs, in which the coils slide over each other,thus permitting greater travel for the same resting length of thespring. In yet another embodiment, actuators 180 are cantilever springsthat bend when compressed. The springs could be made of common materialssuch as metals (steel, titanium, aluminum), polymers, or rubbers. In theembodiment illustrated in FIG. 9, 4 coil springs are located between atop plate 110 and bottom plate 150. The bottom plate 150 may contain theforce, displacement, and angle measurement sensors, a microprocessorpowered by a battery, and a radio for wireless communication.

As illustrated in FIG. 9, the top plate 110 can include a top plateinsertion end 101 in the shape of a portion of a cassini oval. Thegeneral shape may result in each side of the top plate insertion end 101being rounded and including a top plate indent 103 between each roundedside. Similarly, the bottom plate 150 can include a bottom plateinsertion end 153 in the shape of a portion of a cassini oval. Thegeneral shape may result in each side of the bottom plate insertion end153 being rounded and including a bottom plate indent 105 between eachrounded side.

Different configurations of actuators 180 provide advantages anddisadvantages. The choice of a particular configuration of actuators 180may therefore depend on the specific intended use and desired featuresfor the actuation and measurement, which could vary from one surgeon toanother. The use of a mechanical spring as an actuator would allow forthe insert to be an entirely wireless device. Wireless sensors coupledwith constant force springs provide an insert which would not requireany physical connections, and as such could be easily removed andreplaced during the balancing process. In addition, a spring-actuateddevice could be permanently implanted into the joint, whereas otherinserts would need to be removed and then replaced with anidentically-shaped permanent prosthesis. In a further embodiment, theactuators may be locked into a final position and then disconnected fromthe external controller and power source.

FIG. 10 is an alternate exploded view illustration of the insert 100 ofFIG. 9 without the actuators. In the embodiment illustrated, bottomplate 150 includes an electronics recess 162 extending from the outersurface of the bottom plate body 151, opposite the bottom actuatorrecesses 161. The electronics recess 162 may house the electronics board140 and other electronics, such as any sensors, microprocessors, powermodules or radios which communicate the sensed data to. The insert 100may include a bottom plate cover 163 that connects to the bottom platebody 151 and covers the electronics recess 162.

Materials, Shapes and Configurations

The insert 100 may be made from any combination of biocompatible ormedical-grade polymers or metal alloys, as known to one of skill in theart. The biocompatible material may be rated for limited contact. Thematerials would be required to meet structural and mechanicalspecifications needed to sustain the pressures, temperatures, fluids andfrictions with other components of the insert and any adjoining bonesurfaces, cartilage, ligaments and other tissues. The material of thetop plate 110 and in particular of the articular contacting surface 139should be a material that will not damage the articular surface of thefemoral bone or component. The insert 100 should also be made frommaterials which can be sterilized in order to minimize the risk ofinfection during surgery. The material requirements will also apply tothe actuators and in some aspects to the sensors, particularly withregard to the sterilization and durability requirements. In embodiments,the insert 100 may include radiopaque markers or material for use influoroscopic x-ray verification.

The size of the insert 100 may vary depending on the patient or the typeof joint. The insert could conceivably be manufactured in severaldifferent sizes for different sized joints, such as a small, medium andlarge option. In one embodiment, a medium-sized insert would beapproximately 70 millimeters (mm) by 45 mm and have an adjustable heightof 8-14 mm. The height of the insert may need to be adjusted separatelyfrom the actuation mechanism in order to initially fit within the spaceof the joint between opposing bone structures. This may be accomplishedusing shims. In some embodiments, shims include a height from 1-6 mm andmay be provided in 1 mm increments. In embodiments, the articularportion 130 may be switched out for one with a different height for theinitial fit of the insert 100 within the space of the joint. Theactuator 180 could then provide additional movement and spacing of atleast a maximum height change. In one embodiment, the maximum heightchange of the insert is of 4-8 mm. In another embodiment, the maximumheight change is 5-7 millimeters. In yet another embodiment, the maximumheight change is at least 6 mm. The other dimensions of the device mayalso be adjustable in order to better fit a desired shape and size ofthe joint and the adjoining bones, ligaments or cartilage. The insert100 may also be configured to be stable in shear between the top plate110 and the bottom plate 150 throughout the range of motion of the knee.In some embodiments, the stiffness of the bellows under inflation may beconfigured to resist shear. In embodiments, the insert can resist a sideload of 5 lbf. In some embodiments, the range of dynamic knee flexionangle measurement of the insert 100 may be from 10 degrees ofhyperextension to 140 degrees of flexion.

The shape of the insert may also vary depending on the intended use ofthe device. The insert 100 may have a tricompartmental, bicompartmental,or a unicompartmental design. The embodiments illustrated in FIGS. 2 to10 have a tricompartmental design. FIG. 11 is a perspective viewillustration of an embodiment of the insert of FIG. 1 with aunicompartmental configuration. The insert 100 with a unicompartmentaldesign may be essentially half of the tricompartmental design bisecteddown a longitudinal middle of the device. The insert 100 with aunicompartmental design still includes a top plate 110 and a bottomplate 150 separated by one or more actuators. An insert 100 with aunicompartmental design may be advantageous for various types ofsurgical procedures, such as arthroplasty, in particular a partial kneereplacement where only one half of the knee joint is replaced. A partialknee replacement arthroplasty preserves some of the ligaments in theknee, and the insert 100 can be placed on only one half of the joint toallow for balancing of the joint with actuation that similarly avoidsthe need to remove additional ligaments in the knee. The number ofactuators in a partial knee replacement may vary according to userpreference or the specifications of the joint balancing process whenonly part of the knee joint is being replaced.

Multiple inserts 100 with a unicompartmental design may also be utilizedin a full knee replacement where the central cruciate ligaments are tobe preserved by sliding each insert 100 from lateral sides of the kneejoint.

The top plate 110 and the bottom plate 150 may be modular to allow foreasy placement of different types of sensors and actuators. Although theillustrated embodiments of the plates are substantially flat, the platesmay take different shapes to accommodate certain types of sensors,actuators and adjoining bone or other tissue. In one embodiment, theplates may have an elastic property to allow them to slightly deformwhen a load from an adjoining bone is applied (such as that of thefemoral condyles). The elastic plates may be made from rubbers,polyurethane, silastic, gel-filled or air-filled containers.

In some embodiments, the insert may be configured with a rotatingbearing disposed in a central portion of the space between the top plateand the bottom plate. The bearing would provide for the top plate torotate relative to the bottom plate, providing an additional adjustmentthat can be made to better balance the joint. The bearing may beconfigured to provide for approximately 5-10 degrees of rotation of thetop plate with respect to the bottom plate (or vice versa depending onthe configuration of the bearing) or translation from side-to-side andfront-to-back.

The insert may also be configured with only a single plate and a set ofactuators which interface with an opposing bone surface, in oneembodiment of the invention.

Controller

FIG. 12 is an illustration of a perspective view of an embodiment of thecontroller assembly 200 of FIG. 1 connected to an insert 100. In theembodiment illustrated, the insert 100 is a pneumatic insert, such asthe insert 100 of FIGS. 4 and 5. Controller assembly 200 may include acontroller 240, a controller mount 230, and a fluid supply device 220.The controller mount 230 may be a strap or a similar mechanism formounting the controller 240 on to the patient's limb, such as the thigh.In embodiments, the controller mount 230 has a width that is the lengthof controller 240. The controller mount 230 may be affixed to thepatient's limb using a fastener, such as a hook and loop fastener. Theinsert 100 may be connected to the controller 240 by an insertconnection 55. The insert connection 55 may include the fluid supplyline 70 and the electronics connector 60 shown in FIGS. 4 to 7.

The fluid supply device 220 may be an automated source of fluid power,or may be a manually operated source of fluid power, such as a pneumaticsyringe as illustrated in FIG. 12. The fluid supply device 220 may beconfigured to supply fluid, such as a gas, to the controller 240 and tothe insert 100 to actuate the bellows 182 (shown in FIGS. 4 to 6) of theinsert 100. The gas may be air, such as room air, carbon dioxide,nitrogen, or helium. The fluid supply device 220 may be connected to thecontroller 240 by a controller supply line 225. The controller supplyline 225 may be a tube extending from the controller 240 to the fluidsupply device 220. In some embodiments, a pressure relief valve 226 maybe located at the end of controller supply line 225 adjacent controller240. The pressure relief valve 226 may ensure that the pneumaticactuator 180 is not filled above a predetermined maximum pressure, suchas 30 psi.

FIG. 13 is an illustration of a perspective view of the controller 240of the controller assembly 200 of FIG. 12. The controller 240 mayinclude a housing body 241, a housing side 243, and a housing cover 242.The housing body 241 may include the back and three sides of the housingof controller 240. Housing side 243 may attach to an end of housing body241 forming the fourth side of the housing. Housing cover 242 may fastento the housing body 241 and the housing side 243 to form the enclosureof the housing. A button membrane 244 may cover a number of buttons 251(shown in FIG. 15) that are accessible through housing cover 242. Abattery cover 249 may attach to an end of housing body 241, oppositehousing side 243 and may provide access to a battery 248 (shown in FIG.14).

FIG. 14 is an illustration of an exploded view of the controller 240 ofFIG. 13. Housing body 241 may be configured with an electronics chamber253 and an accumulator chamber 252. A battery 248 and controllerelectronics 245 may be housed within electronics chamber 253. Inembodiments, the battery 248 has enough power for the controller 240 tooperate for at least an hour. Controller electronics 245 may include,inter alia, a controller electronics board 250, buttons 251, atransmitting radio, and sensors, such as an angle sensor 254. Controllerelectronics board 250 is in electronic communication with electronicsboard 140, such as wireless or wired communication. In embodiments, theelectronics connector 60 electronically connects and is coupled to thecontroller electronics board 250 and the electronics board 140. Buttons251 may be affixed to controller electronics board 250. The angle sensor254 may provide the angle of the thigh which may indicate the angle ofthe knee flexion. The angle sensor 254 may be an accelerometer, aninclinometer, or a similar device.

The accumulation chamber 252 may smooth out pressure fluctuations as thepneumatic actuator(s) of the insert 100 undergo compression andexpansion. Housing side 243 may form a seal with housing body 241 toprevent leaking from accumulation chamber 252.

Controller 240 may also include a pressure sensor 247 for detecting thepressure of the actuating fluid within accumulation chamber 252, and asensor mount 246 configured to hold pressure sensor 247 in place. Thesensor mount 246 may be sized and shaped to be held within housing body241 by housing side 243. In embodiments the controller 240 also includesa Light emitting diode (LED). The LED may show, inter alia, when thecontroller 240 is activated.

Controller 240 may be fastened to controller mount 230 with a mountingfastener 260. In the embodiment illustrated, mounting fastener is a hookand loop fastener. In other embodiments, other types of fasteners may beused.

In some embodiments, controller functions as a wireless remote and maybe configured to transmit the data from the insert 100, including thevarious sensors and the data from the controller 240, including thepressure sensor 247, to the display system. In other embodiments,controller 240 may also serve as a display device when a suitabledisplay screen is included as part of the controller 240. In furtherembodiments, the controller 240 is directly wired to a display device.

When using the joint balancing system 50, the insert 100 may be placedwithin the appropriate joint (such as the knee joint in this example).The controller 240 may be charged by the surgeon/operator using fluidsupply device 220, such as a pneumatic syringe, to pump up the pressure.In embodiments, the pneumatic syringe is a 20 mL syringe. The pressuremay be monitored by a pressure sensor 247. The pressure may be displayedby the display module 320 in the graphic user interface on a displayscreen. In some embodiments, the optimum pressure is between 20 and 30psi. In some embodiments, the pressure may be modified to exert adefined force. The optimum force may be between 40 and 200 N. Jointbalancing system 50 may be configured to supply pressures at differentranges, depending on the application. With the insert 100 inflated (i.e.bellows expanded under pressure to actuate the insert 100), the knee isflexed (bent) through the full range of available motion. As the knee isflexed, the sensors may measure knee flexion angle, the distance betweenthe top and bottom plates of the insert, and the tilt between the topand bottom plates of the insert. This information may be graphicallydepicted by wired or wireless transmission to the display.

The surgeon can make the appropriate changes to the placement of theartificial components, to the cuts made in the bone, or to the ligamentsof the knee to generate a distraction gap and tilt that is mostdesirable for the patient.

The joint balancing system 50 may be used to balance the knee during asurgical procedure, such as a total knee arthroplasty or a partial kneearthroplasty. The controller mount 230 may be wrapped around a patient'sthigh, such as the lower thigh and tightened firmly. The hook and loopfastener of the controller mount 230 may be placed anteriorly on thethigh. The controller 240 may be aligned with the long axis of thepatient's thigh, with the battery cap 249 and the pressure valve 226facing proximally and the insert connection is facing distally.

The insert 100 may be positioned in between the tibial and femoralsurface. The bottom surface of the bottom plate 150 may be flat and maybe in direct or indirect contact with the tibial bone cut. The uppersurface of the top plate 110 may be curved and may be in direct orindirect contact with the femoral surface. The insert 100 should fitcomfortably and may be centered on the tibial cut surface. The surgeonmay verify that the curved upper surfaces articulate with the femoralcondyles. If the insert 100 cannot be inserted easily, the surgeon mayverify that the gap between the tibial cut surface and the femoralcondyles is at least the height of the insert 100, such as 8 mm. If theinsert 100 is too big or too small for the knee, the surgeon may selectan insert of a different size.

The actuator may then be pressurized by the fluid supply device 220 to apredetermined pressure, such as from 20 psi to 25 psi, and the displaymodule 320 may display the current pressure in the GUI. The insert 100may be expanded from a first predetermined height, such as 8 mm, wherethe insert 100 is not inflated up to a second predetermined height, suchas 14 mm, where the pneumatic actuator is fully inflated. Shims may beused when the tibiofemoral gap is greater than the second predeterminedheight. In other embodiments, the articular portion 130 may beinterchanged with a thicker articular portion 130 when the tibiofemoralgap is greater than the second predetermined height.

Once the insert 100 is positioned in the tibiofemoral gap and inflated,the joint balancing system 50 may be calibrated by holding the knee in0° flexion and selecting a calibration button displayed by the controlmodule on the GUI.

The display module 320 may also display the net gap between the tibialand femoral surfaces in real time. To check gap in flexion andextension: hold the knee in 0° and read the gap off the display. Thenflex the knee to 90° and read the gap off the display. This process canbe repeated as many times as needed. If the surgeon desires to recut thebones or reposition the components, the insert 100 can be removed (afterdeflating the controller). If the surgeon desires to perform soft-tissuereleases and there is sufficient access, he or she can perform thesoft-tissue releases with the insert in place and monitor the changinggap in real-time on the display.

Joint balancing system 50 may also be used to measure the dynamic kneebalance by flexing the knee gently between full extension and fullflexion. The display module 320 may display the net gap between thetibial and femoral surfaces in real time in the GUI as well as recordthe gap and show a plot of the tibiofemoral gap against knee flexion inthe GUI.

The balance of the knee can be changed and monitored in real time byreleasing a ligament with the insert 100 in place and monitoring thechanges in the tibiofemoral gap and tilt while the release is beingperformed. The balance of the knee can also be changed and monitored inreal time by making suitable changes to the femoral or tibial cuts torealign the components.

In some embodiments, the joint balancing system 50 may also include acorrection module. The correction module may interpret the data receivedfrom the insert 100 and the controller 240 and provide recommendationsfor a surgical procedure to correct any perceived imbalance. Thecorrection module may receive other inputs including the bone geometryfrom an imaging modality, such as preoperative CT or MRI scans, theangle between adjacent bony structures, such as the angle between thefemoral and tibial bone shafts, and ligament attachments, which may bebased on digitizing landmarks using surgical navigation instruments.

The correction module may calculate the forces across the articularsurfaces of the insert 210, such as by using rigid bodies to representthe bones and the insert 210, and using springs to represent theligaments. The correction module may refine the ligament attachments,lengths, and stiffnesses to match force displacement data collected ordetermined by the sensors in the joint balancing system 50. Thecorrection module may also calculate corrections to bone cuts and to theligaments based on the lengths, stiffnesses, current angle of bone cuts,and the angle of the tibiofemoral shaft.

If the forces are balanced mediolaterally, but tight in flexion and inextension then the correction module may calculate an amount of bone tobe cut from the proximal tibia based on the force-displacement datacollected in extension and flexion. If forces are acceptable andbalanced mediolaterally in flexion but tight in extension then thecorrection module may calculate an amount of bone to be cut from thedistal femur based on the force versus displacement data collected inextension. The correction module may provide other recommendations, suchas modifications to the ligaments based on the measured data.

Cutting Guides and Grinding Surface

FIGS. 15 and 16 illustrate an embodiment of a joint balancing systemincluding the insert 100 and a cutting guide assembly 400. The cuttingguide assembly 400 connects to the insert 100 that is used to guidecutting bone and tissue during balancing of the joint. Cutting guideassembly 400 may be mounted to the insert 100 to provide a surgeon withguides for cutting sections of bone, cartilage or ligaments during thejoint balancing.

In the embodiment illustrated, a cutting guide assembly 400 includescutting guide mounts 402, a cutting guide 406, and mounting fasteners408, such as pins, screws or bolts. Cutting guide mounts 402 may beattached to the insert 100 at bottom plate 150 or top plate 110.

The cutting guide 406 is attached to the cutting guide mounts 402 usingthe mounting fasteners 408. Cutting guide 406 includes one or moreguiding slots 410. In the embodiment illustrated, cutting guide 406includes two parallel guiding slots 410. The guiding slots 410 can beused to align and make cuts to the bone, cartilage, ligaments or othertissues during the process of balancing the joint and positioning theartificial joint prostheses.

The guiding slots 410 have flat surfaces that hold and guide the bladesof the cutting devices or saws while the surgeon is cutting the bones.The surgeon inserts the cutting saw into the slot of the cutting guide,which helps maintain the location and angle of the guide. In theembodiment described here, the cutting guides are mounted on the platesof the balancing insert such that the cuts are made with the ligamentsappropriately tensioned.

In some embodiment, a surface of the top plate or bottom plate may beconfigured as a grinding (or milling or planing) surface or abrasivesurface so that it operates to grind against a corresponding bonestructure and grind the bone surface into the appropriate shape or asmoother surface.

In some embodiments, such as the embodiments shown in FIGS. 17-40 theinsert 100 includes an integrated mount for a cutting block or guide,such as a tibial cutting guide, a femoral cutting guide, or a posteriorfemoral cutting guide. The insert 100 with the integrated mount and thecutting guide may form a portion of a joint balancing system, such asthe joint balancing systems described herein.

In these embodiments, the insert 100 includes a first plate, a secondplate, and one or more actuators. The second plate is adjacent the firstplate with the one or more actuators located there between. The secondplate includes a plate portion, a transition portion, a mountingportion, and a mounting guide configured to receive the cutting block.The plate portion and the first plate may be substantially parallel andmay be aligned on parallel planes. The transition portion may extendfrom the plate portion protruding beyond the perimeter of the firstplate on one side of the insert 100, such as the front end or the sidethat will be oriented in the anterior direction. The transition portionmay extend parallel to the second plate. The mounting portion may extendfrom the transition portion in a transverse direction relative to thetransition portion and in the direction of the first plate relative tothe second plate and may extend beyond the first plate, such as beyondthe plane of the first plate. The length of the mounting portion may begreater than the distance between the first plate and the second plate.In some embodiments, the mounting portion extends perpendicular to thesecond plate.

In some embodiments, the transition portion includes a bend towards thedirection of the first plate relative to the second plate at the enddistal to the plate portion to transition the direction that the plateportion extends to the direction that the mounting portion extends. Insome embodiments, the mounting guide may include a flange protrudingfrom the mounting portion and may include a bore extending through theflange and the mounting portion. The bore may be sized to receive a pinfor coupling the cutting block or guide to the insert 100.

In the embodiments illustrated, the first plate and the second plate areformed of a rigid material. In other embodiments, the first plate andthe second plate are formed of a non-rigid material that inflates, suchas a bladder or a balloon.

In the embodiment illustrated in FIGS. 17-24, the second plate is thetop plate 110, while the first plate is the bottom plate 150. In theembodiments illustrated in FIGS. 25-40, the second plate is the bottomplate 150, while the first plate is the top plate 110.

FIGS. 17-20 illustrate an embodiment of an insert 100 with an integratedmount for a tibial cutting block. In the embodiment illustrated in FIGS.17-20, the insert 100 is configured for tibial balancing. Referring toFIGS. 17-20, the insert 100 includes a top plate 110, one or moreactuators 180, and a bottom plate 150. The one or more actuators 180 andthe bottom plate 150 may be any of combination of the actuators 180 andbottom plate 150 described above. The top plate 110 includes a topportion 109, a top mounting portion 108, and a top transition portion107. The top portion 109 may include any of the configurations for thetop plate 110 described above and is configured to contact the femur 8,such as at a femoral cut or the femoral condyles 14 (refer to FIG. 2).In the embodiment illustrated, the top portion includes a top plateinsertion end 101. The top portion 109 may also include a top plateindent 103 extending into the top portion 109 from the top plateinsertion end 101. In the embodiment illustrated, the top plate indent103 is a rectangular slot with rounded corners.

The top mounting portion 108 extends downward and beyond the bottomplate 150. The top mounting portion 108 may extend perpendicular to thetop portion 109. In the embodiment illustrated, the top mounting portion108 includes a body 114, a first leg 116, a second leg 117, and an outerrecess 119. The body 114 extends from the top transition portion 107.The legs 116,117 extend downward from the body 114 and may form an outerrecess 119 there between. The first leg 116 may extend down further thanthe second leg 117. The outer recess 119 may assist in mounting thecutting guide, may allow a cut to be made therethrough or may reducematerial costs of the insert 100.

The insert 100 may include one or more mounting guides 192 protrudingfrom the top mounting portion 108. In the embodiment illustrated, eachleg 116,117 of the top mounting portion 108 is rounded and includes amounting guide 192. The mounting guides 192 are configured to receive acutting block, such as cutting guide 406. The cutting block isconfigured with guides or slots for guiding a tibial cut. The mountingguides 192 may include a bore 197 and a flange 191. The bore 197 mayextend through the flange and may extend through the mounting portion108, such as through the leg. The flange 191 may extend and protrude outfrom the mounting portion 108, such as the leg, and may be coaxial tothe bore. Each mounting guide 192 may be configured to receive amounting fastener, such as a pin, a screw, or a bolt. The pins may beused to mount the cutting block to the top plate 110.

The top transition portion 107 may extend outward from the top portion109 in the same general direction as top portion 109, such as extendingparallel to top portion 109, and may extend away from the insertion end101. The top transition portion 107 may curve downward to top mountingportion 108 distal to the top portion 109. In embodiments, toptransition portion 107 curves approximately 90 degrees. As illustrated,top portion 109, top transition portion 107 and top guide portion 108may be formed as an integral piece. The various components of the insert100 may be formed of the materials disclosed herein and may include anyof the material properties disclosed herein. The insert 100 of FIGS.17-20 may include and be coupled with any of the features and componentspreviously described herein, such as sensors, actuators, and the variousembodiments of the top plate 110 and the bottom plate 150. The inset 100of FIGS. 17-20 may also be used in conjunction with the joint balancingsystem 50 described herein or with other types of joint balancingsystems.

FIGS. 21-24 illustrate an alternate embodiment of the insert 100 ofFIGS. 17-20. Referring to FIGS. 21-24, the insert 100 includes anadjustment device 196. The adjustment device 196 may affixed to theinsert 100 at the top mounting portion 108. The adjustment device 196may be configured to adjust the placement of the guide pins located inthe mounting guides 192 based on a comprehensive measurement of relativeangles as well as ligament balance. The adjustment device 196 may be,inter alia, a knob, a screw, a slider, a wheel, an inflatable device, oran inflation mechanism. The adjustment device 196 may be manuallyadjustable or may be adjustable through actuation.

The insert 100 may also include an insert angle sensor 193. The insertangle sensor 193 may also be coupled to the insert 100 at the topmounting portion 108. The insert angle sensor 193 may be used along witha first bone angle sensor 194 that is affixed to the tibia during theprocedure to provide the relative angle between the tibia 10 and theinsert 100 including top plate 110. Adjustments made using theadjustment device 196 may be made at least partially based on the anglebetween the tibia and the insert 100.

In the embodiments illustrated in FIGS. 17-24, the top plate 110articulates with the femoral bone or the femoral component so that thecutting block mounted to the top mounting portion 108 will guide thetibial cut relative to the top late 110 and to the femur 10.

FIGS. 25-28 illustrate an embodiment of an insert 100 with an integratedmount for a femoral cutting block. In the embodiment illustrated inFIGS. 25-28, the insert 100 is configured for tibial balancing and toguide a femoral distal cut. Referring to FIGS. 25-28, the insert 100includes a top plate 110, one or more actuators 180, and a bottom plate150. The top plate and the one or more actuators may be any combinationof the actuators 180 and top plate 110 described above. The bottom plate150 includes a bottom portion 149, a bottom mounting portion 148, and abottom transition portion 147. The bottom portion 149 may include any ofthe configurations for the bottom plate described above and isconfigured to contact the tibia 10, such as a tibial cut (refer to FIGS.29-32). The bottom portion 149 may include a bottom plate insertion end153. The bottom portion 149 may also include a bottom plate indent 105,as shown and described in previous embodiments.

The bottom mounting portion 148 extends upward and beyond top plate 110.The bottom mounting portion 148 may extend perpendicular to the bottomportion 149. The bottom mounting portion 148 may include two legsextending up from the bottom transition portion 147. The two legs may bejoined by a narrow piece of material forming an arch like shape. Eachleg may include a mounting guide 192. The mounting guide 192 isconfigured to receive a cutting block, such as cutting guide 406. Thecutting block is configured with guides or slots for guiding a femoraldistal cut. The mounting guides 192 may include a bore and a flange. Thebore extends through the leg and the flange extends out from the legcoaxial to the bore. Each mounting guide 192 may be configured toreceive a pin. The pins may be used to mount the cutting block to thebottom plate 150.

The bottom transition portion 147 may extend outward from the bottomportion 149 in the same general direction as bottom portion 149, such asextending parallel to bottom portion 149, and may extend away from thebottom plate insertion end 153. The bottom transition portion 147 maycurve upward to bottom mounting portion 148 distal to the bottom portion149. In embodiments, the bottom transition portion 147 curvesapproximately 90 degrees. In the embodiment illustrated, bottomtransition portion 147 includes two legs. Each leg extends from bottomportion 149 to a leg of bottom mounting portion 148. The bottom plate150 including the bottom portion 149, the bottom transition portion 147,and the bottom mounting portion 148 may be formed as an integral piece.The various components of the insert 100 may be formed of the materialsdisclosed herein and may include any of the material propertiesdisclosed herein. The insert 100 of FIGS. 25-28 may include and becoupled with any of the features and components previously describedherein, such as sensors, actuators, and the various embodiments of thetop plate 110 and the bottom plate 150. The inset 100 of FIGS. 25-28 mayalso be used in conjunction with the joint balancing system 50 describedherein or with other types of joint balancing systems.

FIGS. 29-32 illustrate an alternate embodiment of the insert 100 ofFIGS. 25-28. Referring to FIGS. 29-32, the insert 100 includes anadjustment device 196. The adjustment device 196 may affixed to theinsert 100 at the bottom mounting portion 148. The adjustment device 196may be configured to adjust the placement of the guide pins located inthe mounting guides 192 based on a comprehensive measurement of relativeangles as well as ligament balance. The adjustment device 196 may be,inter alia, a knob, a screw, a slider, a wheel, an inflatable device, oran inflation mechanism. The adjustment device 196 may be manuallyadjustable or may be adjustable through actuation.

The insert 100 may also include an insert angle sensor 193. The insertangle sensor 193 may also be coupled to the insert 100 at the bottommounting portion 108. The insert angle sensor 193 may be used along withmultiple bone angle sensors, such as a first bone angle sensor 194 and asecond bone angle sensor 195, that are affixed to adjacent bones, suchas the tibia, femur, and patella, during the procedure to provide therelative angles between adjacent bones, and the insert 100 includingbottom plate 150. In the embodiment illustrated, the first bone anglesensor 195 is affixed to the tibia and the second bone angle sensor 195is affixed to the femur during the procedure to provide the relativeangles between the tibia 10, the femur 8, and the insert 100 includingbottom plate 150. Adjustments made using the adjustment device 196 maybe made at least partially based on these angles.

In the embodiments illustrated in FIGS. 25-32, the bottom plate 110articulates with the tibial bone or the tibial component so that thecutting block mounted to the bottom mounting portion 108 will guide thetibial cut relative to the bottom plate 150 and to the tibia 8.

FIGS. 33-40 illustrate an alternate embodiment of the insert 100 ofFIGS. 25-32. In this embodiment, the insert 100 is configured for tibialbalancing and to guide a femoral posterior cut. The various componentsof the insert illustrated in FIGS. 25-32 may be the same or similar tothe components of the embodiments illustrated in FIGS. 25-32 includingthe top plate 110, the bottom plate 150, and the one or more actuators180. While FIGS. 33-40 do not show the various angle sensors and theadjustment device 196, the insert 100 of FIGS. 33-40 may include thevarious angle sensors and the adjustment device 196. In someembodiments, the lengths and sizes of the bottom transition portion 147and the bottom mounting portion 148 to may differ from other embodimentsto position the cutting block for the femoral posterior cut. In otherembodiments, the cutting block may differ rather than the bottomtransition portion 147 and the bottom mounting portion 148 to positionthe guides of the cutting block for the femoral posterior cut ratherthan the femoral distal cut.

As illustrated in FIGS. 37-40, the knee is in flexion, such as 90degrees flexion when for the femoral posterior cut.

The bottom plate 150 including the bottom portion 149, the bottomtransition portion 147, and the bottom mounting portion 148 may beformed as an integral piece. The various components of the insert 100may be formed of the materials disclosed herein and may include any ofthe material properties disclosed herein. The insert 100 of FIGS. 33-40may include and be coupled with any of the features and componentspreviously described herein, such as sensors, actuators, and the variousembodiments of the top plate 110 and the bottom plate 150. The inset 100of FIGS. 33-40 may also be used in conjunction with the joint balancingsystem 50 described herein or with other types of joint balancingsystems.

A method of cutting a bone during a joint surgery is also disclosed. Inembodiments, such as those disclosed in FIGS. 15-40, the method includesinserting the insert 100 into the joint, such as a knee. The method alsoincludes deploying the actuators, such as inflating the bellows 182. Themethod further includes drilling a hole or holes into the bone, such asthe femur 8 or tibia 10. The pin guides 402 or mounting guides 192 maybe used to guide the drill. The method yet further includes placing apin into each hole(s) in the bone. The pin guides 402 or mounting guides192 may also be used to guide the pin(s) 408 into the bone. The methodstill further includes mounting the cutting guide 406 onto the pins 408as shown in FIG. 16. The cutting guide 406 may be mounted adjacent thepin guides 402 or the mounting portion 108, 148 of the insert 100. Themethod further includes cutting the bone using the guiding slot 410 toguide the cut. The cut may be made parallel to the plate opposite thebone, at a fixed distance from the plate or at a predetermined anglerelative to the plate. For example, in the embodiments shown in FIGS. 15and 25-40 the cut may be made parallel to the bottom plate 150, at afixed distance from the bottom plate 150, or at a predetermined anglerelative to the bottom plate 150. In the embodiments shown in FIGS.17-24 the cut may be made parallel to the top plate 110, at a fixeddistance from the top plate 150, or at a predetermined angle relative tothe top plate 110.

The method may also include adjusting the angle and/or location of thepin guides 402 or the mounting guides 192. Adjusting the angle and/orlocation of the pin guides 402 or the mounting guides 192 may includemanually adjusting or actuating the adjustment device 196. Adjusting theangle and or location of the pin guides 402 or the mounting guides 192may be performed prior to cutting the bone. Each of the steps describedherein may be performed by a medical professional, such as a surgeon.Each of the steps described may be performed in conjunction with themethods and steps for the methods described in conjunction with theembodiments disclosed in FIGS. 1-14. Each of the embodiments of theinsert 100 disclosed in FIGS. 17-10 may be used in conjunction with thejoint balancing system 50 and with the methods for using the jointbalancing system 50.

FIGS. 41-48 illustrate an embodiment of a femoral cutting guide 500. Inthe embodiment illustrated, femoral cutting guide 500 is a distalfemoral cutting guide. Cutting guide 500 includes a guide body 520, ablade guiding feature 524, and a guide rod 510. The guide body 520includes a bottom portion 521, a front portion 522, and a transitionportion 523. Bottom portion 521 may have a plate like shape. Bottomportion 521 may include an insertion end 525. The insertion end 525 maybe rounded on each side and may include an indent 526. In embodiments,the insertion end 525 includes the shape of a portion of a cassini ovalto form the rounded sides 527 and the indent 526.

Transition portion 523 may extend away from bottom portion 521 in thedirection opposite the insertion end 525 and curve upward to frontportion 522. Transition portion 523 may be a plate with an arcuate shapeand may curve approximately 90 degrees.

Front portion 522 may extend in a direction transverse to the directionthat bottom portion 521 extends, such as perpendicular to bottom portion521. Front portion 522 may include a top edge 528. Top edge 528 may bedistal to transition portion 523. Top edge 528 may be curved. In theembodiment illustrated, top edge 528 has an asymmetric curve with theapex shifted toward one side so that one side is higher than the other.

Guide body 520 may include a front face 529. Front face 529 may be thesurface facing opposite the direction of insertion end 525 and mayinclude the outer surface of front portion and part of the outer surfaceof transition portion 523.

Blade guiding feature 524 may be a slot or a similar feature configuredto guide the distal femoral cut. Blade guiding feature 524 may belocated in the guide body 520 and may be adjacent the distal end oftransition portion 523.

The guide rod 510 extends from the guide body 520. In the embodimentillustrated, guide rod 510 extends up from bottom portion 521 in thesame general direction that transition portion 523 curves towards. Guiderod 510 is configured to be inserted into the intramedullary canal ofthe femur 8. The guide rod 510 may be shaped to match the shape of theintramedullary canal of the femur 8.

Guide rod 510 includes a base 511 and an end 512. The base 511 adjoinsbottom portion 521 and the end 512 is distal to bottom portion 521. Thebase 511 may be larger than the end 512 with the guide rod 510 taperingdown from the base 511 to the end 512. The guide rod 510 may have anarcuate shape. In the embodiment illustrated, guide rod 510 extends upin an initial direction that is less than ninety degrees relative tobottom portion 521 and may curve towards extending in a direction thatis closer to ninety degrees relative to bottom portion 521 than theinitial direction.

Femoral cutting guide 500 may also include a cutting guide adjustmentdevice 530, a cutting guide sensor 540, and one or more bone anglesensors 545. The bone angle sensor(s) 545 may be affixed to the bonestructures adjacent the joint, such as the femur, tibia, or the patella.In the embodiment illustrated, the bone angle sensor 545 is located onthe femur. The cutting guide adjustment device 530 may be used to adjustthe angle of the femoral cutting guide 500 relative to the femur 8 andadjust the location of blade guiding feature 524. The cutting guideadjustment device 530 may be, inter alia, a knob, a screw, a slider, awheel, an inflatable device, or an inflation mechanism. The cuttingguide adjustment device 530 may be manually adjustable or may beadjustable through actuation. The cutting guide sensor 540 may be usedwith the bone angle sensor(s) 545 to measure the angle between thefemoral cutting guide 500 and the femur 8. The cutting guide sensor 540may be affixed to the guide body 520 at the front surface 529. In theembodiment illustrated, the cutting guide sensor 540 is affixed to theguide body 520 adjacent to the apex of the top edge 528. The bone anglesensor(s) 545 may be separate from the guide body 520 and may be affixedto the femur 8 while the femoral cutting guide 500 is in place, such aswhile the guide rod 510 is located in the intramedullary canal of thepatient.

Femoral cutting guide 500 may be a custom guide that is created specificto the patient. The exact measurements of the various components may bebased on various images taken of the joint of the patient, such as theimages from x-rays, CT scans, MRIs, and the like. After measuring thepatient's joint and creating the femoral cutting guide 500, the guiderod 510 is then inserted into the intramedullary canal of the patient'sfemur. The angle between the femur 8 and the femoral cutting guide 500may then be measured. The cutting guide adjustment device 530 may thenbe used to properly position the femoral cutting guide 500 relative tothe femur 8. Once femoral cutting guide 500 is properly positioned, suchas being at a predetermined angle relative to the femur 8, the distalfemoral cut is made using a cutting tool, such as a saw blade.

FIGS. 49-52 illustrate an embodiment of the femoral cutting guide 500 ofFIGS. 41-48 after the distal femoral cut is made. The femoral cuttingguide of FIGS. 49-52 may include the various angle sensors and cuttingguide adjustment device shown in FIGS. 41-48. As illustrated, the distalfemoral cut 9 is parallel to the blade guiding feature 524. After thedistal femoral cut 9 is made an insert 100 may be used to balance thejoint and to make additional cuts to the femur 8 or to the tibia.

The guide rod 510 and the guide body 520 may be formed as an integralpiece. The various components of the femoral cutting guide 500 may beformed of the materials disclosed herein and may include any of thematerial properties disclosed herein.

A method for performing a femoral cut using the femoral cutting guide500 is also disclosed. In embodiments, the method includes inserting theguide rod 510 into the intramedullary canal of the femur 8. The guiderod 510 may be inserted so that the guide rod 510 is aligned with thelong axis of the femoral shaft. The method also includes cutting thebone at a fixed angle relative to the guide rod 510.

The method may include affixing a bone angle sensor 545 to the femur 8.The method may also include measuring the angle between the cuttingguide sensor 540 affixed to the femoral cutting guide and the bone anglesensor 545. The method may yet further include adjusting the angle andposition of the blade guiding feature 524. In some embodiments,adjusting the angle and position of the blade guiding feature 524relative to the femur 8 includes manually adjusting or actuating theadjustment device 530 until the blade guide feature 524 is at thepredetermined angle for the cut.

FIGS. 53-60 illustrate an embodiment of a distal femoral balancer 600.The distal femoral balancer 600 may be configured to balance the femurrelative to the tibial surface. The balancing may be performed beforeand after the distal femoral cut. The distal femoral balancer includes afirst condyle portion 610 and a second condyle portion 620. The firstcondyle portion 610 includes a first outer surface 611, a first innersurface 619, a first front portion 612, and a first bottom portion 613.The first outer surface 611 is configured to resemble the surface offemoral condyle and the first inner surface 619 may be configured toreceive a femoral condyle and may generally match the shape of thefemoral condyle. The first front portion 611 extends up and isconfigured to be anterior to the femoral condyle, while the first bottomportion 612 extends from the first front portion 611 and is configuredto be inferior to the femoral condyle.

The second condyle portion 620 includes a second outer surface 621, asecond inner surface 629, a second front portion 622, and a secondbottom portion 623. The second outer surface 621 is configured toresemble the surface of femoral condyle and the second inner surface 629may be configured to receive a femoral condyle and may generally matchthe shape of the femoral condyle. The second front portion 621 extendsup and is configured to be anterior to the femoral condyle, while thesecond bottom portion 622 extends from the second front portion 621 andis configured to be inferior to the femoral condyle.

The first outer surface 611 and the second outer surface 621 may bemodeled after the femoral condyles of the patient's femur.

The distal femoral balancer 600 may also include pin guides 630. A pinguide 630 may be located on each of the first condyle portion 610 and onthe second condyle portion 620. In the embodiment illustrated, a pinguide 630 is located on the first front portion 611 and a pin guide islocated on the second front portion 621. The pin guides 630 may includea bore 632 and a flange 631. The bore extends through the condyleportion and the flange extends out from the condyle portion and may becoaxial to the bore 632. Each pin guide 630 may be configured to receivea pin and guide pins into the femur 8. The pins may then be used to makea femoral cut after the distal femoral balancer 600 is removed and acutting block is mounted to the femur via the pins.

Referring to FIG. 59, the distal femoral balancer 600 may include abalancer actuator 640 for balancing the joint. In the embodimentillustrated, the balancer actuator 640 is configured to be locatedbetween the two femoral balancer portions and the distal femoral cut 9.In embodiments where the distal femoral balancer 600 is used prior tothe distal femoral cut 9, the femoral balancer actuator 640 isconfigured to be located between the two femoral balancer condyleportions and the femoral condyles. In embodiments, the balancer actuatorincludes multiple actuators, such as one actuator between each condyleportion and the adjacent femoral condyle.

In some embodiments, the distal femoral balancer 600 includes a bladeguiding feature for making a distal femoral cut, similar to the bladeguiding feature of femoral cutting guide 500.

The first condyle portion 610, the second condyle portion 620, and thepin guides 630 may be formed as an integral piece. The variouscomponents of the distal femoral balancer 600 may be formed of thematerials disclosed herein and may include any of the materialproperties disclosed herein.

The distal femoral balancer 600 may be used to balance the joint. Inembodiments, the method includes making a distal femoral cut. Any of thecutting methods and tools described herein may be used to make the cut.In some embodiments, the method includes removing the insert 100 aftermaking the cut. The method also includes placing the distal femoralbalancer on the distal femoral cut and deploying the distal femoralbalancer 600 to distract the joint. Placing the distal femoral balancer600 may include locating the distal femoral balancer 600 as shown in thefigures and as described herein. The method further includes formingholes into the bone, such as the femur, and placing pins, such as thepins 402 illustrated in FIGS. 15-16, into the holes. The pin guides 630may be used to make the holes and to place the pins. In embodiments,placing the pins includes locating the pins at a fixed distance and at afixed angle from the bottom portion of the distracted device. The methodmay also include mounting a cutting block 400 to the pins and using theguiding slot 410 to make a second cut to the bone.

FIGS. 61-68 illustrate an embodiment of a posterior femoral balancer700. The posterior femoral balancer 700 is configured to balance thefemur 8 in flexion, such as 90 degrees of flexion relative to the tibia.The posterior femoral balancer 700 may be configured to adjust theposterior femoral cuts relative to the tibia and to the distal femoralcut 9. The posterior femoral balancer 700 includes a balancer body 710,a first posterior condyle portion 720, a second posterior condyleportion 730, and posterior pin guides 740.

Balancer body 710 may include a connection portion 711, a first leg 712,and a second leg 713. The connection portion 711 may be a narrow neckconnecting the first leg 712 to the second leg 713. The connectionportion 711 may be a narrow piece of material forming plate with an archlike shape. The first leg 712 and the second leg 713 are configured toextend along the distal femoral cut 9. The balancer body 710 maygenerally have a ‘U’ shape formed by the connection portion 711, thefirst leg 712 and the second leg 713. The connection portion 711, thefirst leg 712 and the second leg 713 may form a rounded slot therebetween.

The first leg 712 may include a first rounded end 714 adjacent theconnection portion 711 and distal to the first posterior condyle portion720. The second leg 712 may include a second rounded end 715 that isadjacent the connection portion 711 and distal to the second posteriorcondyle portion 730. In some embodiments, the second rounded endprotrudes further from the second posterior condyle portion 730 than thefirst rounded end 714 extends from the first posterior condyle portion720. The first rounded end 714 and the second rounded end 715 extendfurther than the connection portion 711 forming an indent 716 therebetween.

The first posterior condyle portion 720 extends up from balancer body710 in a direction transverse to the direction that the balancer body710 extends and may be perpendicular to the balancer body 710. The firstposterior condyle portion 720 may extend from the first leg 712. Thefirst posterior condyle portion 720 may include a first posterior innersurface and a first posterior outer surface 721. The first posteriorinner surface 722 may be a flat surface and may be adjacent theposterior femoral cut. The first posterior outer surface 721 mayresemble the posterior of a femoral condyle.

The second posterior condyle portion 730 extends up from balancer body710 in the same direction as the first posterior condyle portion 710, adirection transverse to the direction that the balancer body 710extends, and may be perpendicular to the balancer body 710. The secondposterior condyle portion 730 may extend from the second leg 713. Thesecond posterior condyle portion 730 may include a second posteriorinner surface and a second posterior outer surface 731. The secondposterior inner surface 732 may be a flat surface and may be adjacentthe posterior femoral cut. The second posterior outer surface 731 mayresemble the posterior of a femoral condyle.

The first posterior outer surface 721 and the second posterior outersurface 731 may be modeled after the posterior portions of the femoralcondyles of the patient's femur.

The posterior pin guides 740 may be located on each leg of the balancerbody 710. The posterior pin guides 740 may include a bore 742 and aflange 741. The bore 742 extends through the balancer body 710, such asthrough one of the legs. The flange 741 extends out from the balancerbody 710, such as from one of the legs. In embodiments, the flange 741is coaxial to the bore 742. Each posterior pin guide 740 may beconfigured to receive a pin and guide pins into the femur 8 at thedistal femoral cut 9. The pins may then be used to make a posteriorfemoral cut after the posterior femoral balancer 700 is removed and acutting block is mounted to the femur via the pins. In some embodiments,each posterior pin guide includes a second flange 743 extending inward,coaxial to the bore 742.

Referring to FIG. 67, the posterior femoral balancer 700 may include aposterior balancer actuator 750. In the embodiment illustrated, theposterior balancer actuator 750 may adjoin the first and second innersurfaces and may adjoin the posterior femoral cut 7. The balanceractuator 750 locates between the first and second posterior condyleportions 720 and 730 and the femur, such as at the posterior femoral cut7. In embodiments, the posterior balancer actuator 750 includes multipleactuators, such as an actuator between the first posterior condyleportion 720 and the posterior femoral cut 7 and an actuator between thesecond posterior condyle portion 730 and the posterior femoral cut 7.Once a balance is achieved based on predetermined conditions, pins areinserted into the femur 8 at the distal femoral cut 9 through theposterior pin guides 740. The posterior femoral balancer 700 is thenremoved and a cutting block is mounted to the femur via the pins. Theposterior femoral cuts may then be adjusted using the cutting block,such as cutting block 400.

In some embodiments, the posterior femoral balancer 700 can be mountedto the femur before any posterior femoral cuts are made. In theseembodiments, the first and second posterior condyle portions 720 and 730are contoured to fit the uncut femoral condyles of the patient's knee.

The balancer body 710, the first posterior condyle portion 720, thesecond posterior condyle portion 730, and the posterior pin guides 740may be formed as an integral piece. The various components of theposterior femoral balancer 700 may be formed of the materials disclosedherein and may include any of the material properties disclosed herein.While the posterior femoral balancer 700 is described in relation tobalancing the posterior of the femoral component of the knee joint, theposterior femoral balancer 700 may be used in balancing the posterior ofother bone components and may be used in the balancing of other joints.

The posterior femoral balancer 700 may also be used to balance thejoint. In embodiments, the method includes making a posterior femoralcut. Any of the cutting methods and tools described herein may be usedto make the cut. In some embodiments, the method includes removing theinsert 100 after making the cut. The method also includes placing theposterior femoral balancer 700 on the posterior femoral cut anddeploying the posterior femoral cut to distract the joint. Placing theposterior femoral balancer 700 may include locating the posteriorbalancer 700 as shown in the figures and as described herein. The methodfurther includes forming holes into the bone, such as the femur, andplacing pins, such as the pins 402 illustrated in FIGS. 15-16, into theholes. The pin guides 740 may be used to make the holes and to place thepins. In embodiments, placing the pins includes locating the pins at afixed distance and at a fixed angle from the bottom portion of thedistracted device. The method may also include mounting a cutting block400 to the pins and using the guiding slot 410 to make a second cut tothe bone.

FIGS. 69-76 illustrate an embodiment of a whole femoral balancer 800.The whole femoral balancer 800 is configured to balance the alignment ofthe entire femoral component simultaneously. The shape of the wholefemoral balancer 800 may generally be configured to resemble thecondyles of a femur 8, such as the patient's femur. The whole femoralbalancer 800 may wrap around the end of the femur 8 from the anterioraround the distal end to the posterior of the femur. In embodiments, thewhole femoral balancer 800 wraps approximately 270 degrees around thefemur 8.

The whole femoral balancer 800 includes an anterior portion 810, adistal portion 820, and a posterior portion 830. The anterior portion810 is configured to be adjacent the anterior of the femur 8, such asadjacent the anterior femoral cut. The anterior portion 810 may beconfigured to extend around a chamfer cut to the distal portion 820. Theanterior portion 810 may include an anterior edge 804. The anteriorportion may extend from the anterior edge in a first direction andtransition into a second direction that is transverse to the firstdirection.

The distal portion 820 extends from the anterior portion 810 and islocated between the anterior portion 810 and the posterior portion 830.The distal portion 820 may extend in the second direction from theanterior portion 810. The distal portion 820 may include a first distalleg 821 and a second distal leg 822 adjacent the posterior portion 830to follow the shape of two condyles. In some embodiments, the distalportion 820 separates into the two legs. In other embodiments, eachdistal leg extends from the anterior portion 810. The distal portion 820is configured to be adjacent the distal end of the femur 8, such asadjacent the distal femoral cut.

The posterior portion 830 extends from the distal portion 820 and mayextend in the same general direction as anterior portion 810. Theposterior portion 830 may include a posterior first condyle portion 831and a posterior second condyle portion 832. The posterior first condyleportion 831 extends from the distal portion 820 and may extend from thefirst distal leg 821. The posterior second condyle portion 832 extendsfrom the distal portion 820 and may extend from the second distal leg822.

The whole femoral balancer 800 may also include anterior pin guides 815and distal pin guides 825. The anterior pin guides 815 are located atthe anterior portion 810. The anterior pin guides 815 may include a bore807 and a flange 806. The bore 807 extends through the anterior portion810 and the flange 806 extends out from the anterior portion 810 coaxialto the bore 807. Each anterior pin guide 815 may be configured toreceive a pin and guide pins into the anterior of the femur 8. The pinsmay then be used to make a femoral cut after the whole femoral balancer800 is removed and a cutting block is mounted to the femur via the pins.

The distal pin guides 825 are located at the distal portion 810. Thedistal pin guides 825 may include a bore 809 and a flange 808. The bore809 extends through the distal portion 820 and the flange 808 extendsout from the distal portion 820 coaxial to the bore 809. Each distal pinguide 825 may be configured to receive a pin and guide pins into thedistal end of the femur 8. The pins may then be used to make a femoralcut after the whole femoral balancer 800 is removed and a cutting blockis mounted to the femur via the pins.

The anterior portion 810 may include an anterior inner surface 814 andan anterior outer surface 813. The anterior inner surface 814 may adjointhe anterior portion of the femur 8 and may be a flat surface. Theanterior inner surface 814 may extend in the first direction. Theanterior outer surface 813 may include rounds that form the generalshape of the anterior of the femoral component. The anterior portion 810may also include an anterior chamfer surface 804. The anterior chamfersurface may be adjacent the anterior inner surface and adjacent thedistal portion 820. The anterior chamfer surface 804 may extend at aforty-five degrees angle relative to the anterior inner surface 814.

The distal portion 820 may include a distal inner surface 824 and adistal outer surface 823. The distal inner surface 824 may be a flatsurface. The distal inner surface 824 may be perpendicular to theanterior inner surface 814. The distal outer surface 823 may includerounds to form the general shape of the distal end of the femur 8 andmay match the shape of the distal end of the femoral component. Each ofthe first and second leg may include a distal inner surface 824 and adistal outer surface 823.

The posterior portion 830 may include a posterior inner surface 834 anda posterior outer surface 833. The posterior inner surface 834 may be aflat surface and may locate adjacent the posterior portion of thecondyles. The posterior inner surface 834 may be parallel to theanterior inner surface 814. The posterior outer surface 833 may includethe general shape of the posterior portion of the femur and may matchthe shape of the posterior of the femoral component. Each of theposterior condyle portions may include a posterior inner surface 834 anda posterior outer surface 833. The posterior portion 830 may alsoinclude a posterior chamfer surface 803. The posterior chamfer surface824 may extend from the distal inner surface 824 to the posterior innersurface 834. The posterior chamfer surface 803 may be angled atforty-five degrees relative to the distal inner surface 824 and theposterior inner surface 834.

Each inner surface of the whole femoral balancer 800 may be parallel toa femoral cut or chamfer.

The anterior portion 810, the distal portion 820, the posterior portion830, the anterior pin guides 815, and the distal pin guides 825 may beformed as an integral piece of material. The various components of wholefemoral balancer 800 may be formed of the materials disclosed herein andmay include any of the material properties disclosed herein.

Referring to FIG. 75, the whole femoral balancer 800 may also include ananterior actuator 818, a distal actuator 828, and a posterior actuator838. The anterior actuator 818 may adjoin and may be joined to theanterior inner surface 814. The anterior actuator 818 locates betweenthe anterior portion 810 and the anterior of the femur 8. In someembodiments, the anterior actuator includes multiple actuators.

The distal actuator 828 may adjoin and may be joined to the distal innersurface 824. The distal actuator 828 locates between the distal portion820 and the distal end of the femur 8. In some embodiments, the distalactuator 828 includes multiple actuators, such as an actuator betweeneach leg and the distal end of the femur 8.

The posterior actuator 838 may adjoin and may be joined to the posteriorinner surface 834. The posterior actuator 838 locates between theposterior portion 830 and the posterior of the femur 8. In someembodiments, the posterior actuator 838 includes multiple actuators,such as an actuator between each posterior condyle portion.

The actuators may balance the alignment of the entire femoral component.After a predetermined condition of the whole femoral balancer isachieved with the actuators, pins are placed into femur 8 through theanterior pin guides 815 and the distal pin guides 825. In someembodiments, the whole femoral balancer 800 can include other actuators,such as actuators that are configured to be located adjacent the chamfercuts 5.

In some embodiments, the whole femoral balancer may include one or moreblade guiding feature, such as a slot, that can serve as a cutting guidefor a cutting instrument.

FIGS. 77-80 illustrate an alternate embodiment of the whole femoralbalancer 800 of FIGS. 69-76. In the embodiment illustrated, the anteriorportion 810 includes an end portion 855 and a middle portion 850. Theupper portion 855 is configured to be located at the anterior of thefemoral component. Middle portion 850 is configured to transitionbetween the upper portion 855 and the distal portion 820. The middleportion 850 may be adjacent a chamfer cut 5.

The whole femoral balancer 800 may include a first transition portion812 and a second transition portion 832. End portion 855 may be joinedto middle portion 850 by first transition portion 812 and middle portion850 may be joined to distal portion 820 by second transition portion832. In the embodiment illustrated, anterior portion 810, distal portion820, and posterior portion 830 are an integral piece. In otherembodiments, upper portion 855 and middle portion 850 are separatepieces, and distal portion 820 and posterior portion 830 are a separatepiece with the pieces linked together. First transition portion 812 mayinclude a link that joins end portion 855 and middle portion 850together. Second transition portion 832 may include a link that joinsmiddle portion 850 to distal portion 820. Distal portion 820 andposterior portion may be a separate piece. In some embodiments, thefirst distal leg 821 and the posterior first condyle portion 931 formone piece and the second distal leg 822 and the posterior second condyleportion 832 form another piece.

The whole femoral balancer includes an anterior adjustment device 817and a distal adjustment device 827. The anterior adjustment device 817and the distal adjustment device 827 may be, inter alia, a knob, ascrew, a slider, a wheel, an inflatable device, or an inflationmechanism. The anterior adjustment device 817 and the distal adjustmentdevice 827 may be manually adjustable or may be adjustable throughactuation. The anterior adjustment device 817 may be affixed to anteriorportion 810, such as between end portion 855 and middle portion 850 atfirst transition portion 812. Anterior adjustment device 817 isconfigured to adjust the angle between the whole femoral balancer 800and the femur 800 and in particular may be configured to adjust theanterior portion 810 relative to the femoral cuts.

The distal adjustment device 827 may be affixed between middle portion850 and distal portion 820 at second transition portion 832. Distaladjustment device 827 is configured to adjust the angle between thewhole femoral balancer 800 and the femur 800 and in particular may beconfigured to adjust the middle portion 850, the distal portion 820, andthe posterior portion 830 relative to the femoral cuts.

The whole femoral balancer 800 may also include an anterior sensor 816mounted on the anterior portion 810 and a distal sensor 826 mounted onthe distal portion 820. In the embodiment illustrated, the distal sensor826 is configured to be located adjacent the distal end of the femur 8.The anterior sensor 816 and the distal sensor 826 may be used inconjunction with one or more bone angle sensor(s) 840 to determine theangle between adjacent bone structure(s), such as the tibia 10, thefemur 8, or the patella, and the whole femoral balancer 800. Theanterior adjustment device 817 and the distal adjustment device 827 maythen be used to adjust the whole femoral balancer until the angles fallwithin predetermined values that signify a balanced condition.

The whole femoral balancer 800 may also include a number of relief slots805 located adjacent the first transition portion 812 between endportion 855 and middle portion 850, and adjacent the second transitionportion 832 between middle portion 850 and distal portion 820. Therelief slots 805 may reduce the rigidity of the whole femoral balancer800 and may reduce the effects of the anterior adjustment device 817 onthe distal portion 820 and the effects of the distal adjustment device827 on the anterior potion 810. The embodiment illustrated in FIGS.77-80 also includes an anterior actuator 818, a distal actuator 828, anda posterior actuator 838. In embodiments, the actuators are used toobtain an initial balance of the whole femoral balancer 800. Theadjustment devices may then be used in conjunction with the anglesensors to adjust the relative position of anterior portion 810, distalportion 820, and posterior portion 830 to refine the balance of thewhole femoral balancer 800. While the whole femoral balancer 800 isdescribed in conjunction with balancing the knee joint and in particularthe femur, the whole femoral balancer 800 can be used in the balancingof other joints and of other bone structures.

The whole femoral balancer 800 may also be used to balance the joint. Inembodiments, the method includes placing the whole femoral balancer 800over the femoral component. Placing the whole femoral balancer 800 mayinclude locating the whole femoral balancer 800 as shown in the figuresand described herein. The method also includes cutting the bone, such asperforming anterior, distal and posterior cuts to the femoral component.The cuts may be made before or after placing the whole femoral balancer800 over the femoral component. The method also includes deploying thewhole femoral balancer 800 to distract the joint.

The method may also include forming holes into the bone, such as intothe femur, and placing pins, such as the pins illustrated in FIGS.15-16, into the holes. The pin guides 815 and 825 may be used to makethe holes and to place the pins. One or more sets of holes may be formedand one or more sets of pins may be placed in the holes. In embodiments,placing the pins includes locating the pins at a fixed distance and at afixed angle from a predetermined portion of the distracted device. Themethod may also include mounting a cutting block 400 to the pins or toone set of pins and using the guiding slot 410 to make a cut to thebone. The method may also include mounting a second cutting block 400 toanother set of pins and making another cut to the bone.

In some embodiments, the method includes adjusting the relative angleand position of all or a portion of the whole femoral balancer, such asthe anterior portion 810 or the distal portion 820. Adjusting therelative angle and position of all or a portion of the whole femoralbalancer may include manually adjusting or actuating the anterioradjustment device and/or the distal adjustment device 827. In someembodiments, the method also includes measuring the angle of all or aportion of the whole femoral balancer 800 relative to the bone, such asthe femur 8. Measuring the angle of all or a portion of the wholefemoral balancer relative to the bone may include measuring the relativeangle between the anterior sensor 816 and the bone sensor 840 andmeasuring the relative angle between the distal sensor 826 and the bonesensor 840. Other sensors, such as a sensor located on the posteriorportion 830 may also be used. The method may include affixing a bonesensor 840 to the bone. The step of adjusting the relative angle andposition of the whole femoral balancer may be performed prior to makingthe cuts.

Those of skill will appreciate that the various illustrative logicalblocks, modules, and algorithm steps described in connection with theembodiments disclosed herein can be implemented as electronic hardware,computer software, or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, and steps have been described abovegenerally in terms of their functionality. Whether such functionality isimplemented as hardware or software depends upon the design constraintsimposed on the overall system. Skilled persons can implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the invention. In addition, the grouping offunctions within a module, block, or step is for ease of description.Specific functions or steps can be moved from one module or blockwithout departing from the invention.

The various illustrative logical blocks and modules described inconnection with the embodiments disclosed herein can be implemented orperformed with a general purpose processor, a digital signal processor(DSP), application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor can be a microprocessor, but in thealternative, the processor can be any processor, controller,microcontroller, or state machine. A processor can also be implementedas a combination of computing devices, for example, a combination of aDSP and a microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theembodiments disclosed herein can be embodied directly in hardware, in asoftware module executed by a processor (e.g., of a computer), or in acombination of the two. A software module can reside in RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, harddisk, a removable disk, a CD-ROM, or any other form of storage medium.An exemplary storage medium can be coupled to the processor such thatthe processor can read information from, and write information to, thestorage medium. In the alternative, the storage medium can be integralto the processor. The processor and the storage medium can reside in anASIC.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notof limitation. The breadth and scope should not be limited by any of theabove-described exemplary embodiments. Where this document refers totechnologies that would be apparent or known to one of ordinary skill inthe art, such technologies encompass those apparent or known to theskilled artisan now or at any time in the future. In addition, thedescribed embodiments are not restricted to the illustrated examplearchitectures or configurations, but the desired features can beimplemented using a variety of alternative architectures andconfigurations. As will become apparent to one of ordinary skill in theart after reading this document, the illustrated embodiments and theirvarious alternatives can be implemented without confinement to theillustrated example. One of ordinary skill in the art would alsounderstand how alternative functional, logical or physical partitioningand configurations could be utilized to implement the desired featuresof the described embodiments. Hence, although the present disclosure,for convenience of explanation, depicts and describes an insert forbalancing a knee joint, it will be appreciated that the insert inaccordance with this disclosure can be implemented in various otherconfigurations and can be used to balance various other types of joints,such as hip, shoulder, ankle, elbow, and spine joints.

Furthermore, although items, elements or components may be described orclaimed in the singular, the plural is contemplated to be within thescope thereof unless limitation to the singular is explicitly stated.The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other like phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent.

What is claimed is:
 1. An insert for balancing a joint during repair ofthe joint, the insert comprising: a first plate configured to interfacewith a bone structure of a joint; a second plate including a plateportion spaced apart from the first plate and configured to interfacewith an opposing bone structure of the joint, a transition portionextending from the plate portion protruding beyond the perimeter of thefirst plate, and a mounting portion extending in a transverse directionrelative to the transition portion in the direction of the first plate;and an actuator located between the first plate and the plate portionand configured to apply a force to the first plate and to the plateportion.
 2. The insert of claim 1, further comprising a plurality ofsensors for determining a spatial relationship between the first plateand the plate portion.
 3. The insert of claim 1, wherein the first plateis a bottom plate configured to contact a tibia during repair of thejoint, and the second plate is a top plate where the plate portion isconfigured to contact a femur during repair of the joint and themounting portion extends down beyond the bottom plate.
 4. The insert ofclaim 1, wherein the first plate is a top plate configured to contact afemur during repair of the joint, and the second plate is a bottom platewhere the plate portion is configured to contact a tibia during repairof the joint and the mounting portion extends up beyond the top plate.5. The insert of claim 1, wherein the actuator is a pneumatic actuatorincluding a bellows made of an inflatable material, the bellowsconfigured to inflate and pneumatically apply the force to the firstplate and to the plate portion.
 6. The insert of claim 1, wherein thesecond plate includes a mounting guide, the mounting guide including aflange protruding from the mounting portion.
 7. A joint balancing systemfor balancing the joint during repair of the joint including the insertof claim 7, the joint balancing system further comprising: a cuttingguide including a guiding slot configured to guide a cut during therepair of the joint; and a mounting fastener that couples the cuttingguide to the mounting portion, wherein the mounting fastener extendsinto the flange.
 8. The joint balancing system of claim 7, wherein themounting fastener is a guide pin, and wherein the insert includes anadjustment device affixed to the mounting portion configured to adjust aplacement of the guide pin.
 9. An insert for balancing a joint duringrepair of the joint, the insert comprising: a bottom plate configured tointerface with a bone structure of a joint; a top plate including a topportion spaced apart from the bottom plate and configured to interfacewith an opposing bone structure of the joint, a top transition portionextending from the top portion in the general direction of the topportion, and a top mounting portion extending downward from the toptransition portion beyond the bottom plate; and an actuator locatedbetween the bottom plate and the top portion for distributing a force tothe bottom plate and to the top portion.
 10. The insert of claim 8,further comprising a plurality of sensors for determining a spatialrelationship between the bottom plate and the top portion.
 11. Theinsert of claim 8, wherein the top mounting portion further comprises: abody extending downward from the top transition portion; a first legextending downward from the body; a second leg extending downward fromthe body adjacent to the second leg forming an outer recess therebetween; a first mounting portion protruding from the first leg; and asecond mounting portion protruding from the second leg.
 12. The insertof claim 11, wherein the first leg extends further than the second leg.13. The insert of claim 8, wherein the top plate includes a mountingguide, the mounting guide including a flange protruding from the topmounting portion, the insert further comprising an adjustment deviceaffixed to the top mounting portion for adjusting a placement of a guidepin.
 14. A joint balancing system for balancing the joint during repairof the joint including the insert of claim 8, the joint balancing systemfurther comprising: a first bone angle sensor for affixing to the tibiaduring repair of the joint; and an insert angle sensor coupled to theinsert.
 15. An insert for balancing a joint during repair of the joint,the insert comprising: a top plate configured to interface with a bonestructure of a joint; a bottom plate including a bottom portion spacedapart from the top plate and configured to interface with an opposingbone structure of the joint, a bottom transition portion extending fromthe bottom portion in the general direction of the bottom portion, and abottom mounting portion extending upward from the bottom transitionportion beyond the top plate; and an actuator located between the topplate and the bottom portion for distributing a force to the top plateand to the bottom portion.
 16. The insert of claim 15, furthercomprising a plurality of sensors for determining a spatial relationshipbetween the top plate and the bottom portion.
 17. The insert of claim15, wherein the bottom transition portion includes a first transitionleg extending from the bottom portion and a second transition legextending from the bottom portion; and wherein the bottom mountingportion further comprises: a first leg extending upward from the firsttransition leg, a second leg extending upward from second transition legand joined to the first leg at the distal end of the bottom mountingportion, a first mounting portion protruding from the first leg, and asecond mounting portion protruding from the second leg.
 18. The insertof claim 17, wherein the first leg extends further than the second leg.19. The insert of claim 15, wherein the bottom plate includes a mountingguide, the mounting guide including a flange protruding from the bottommounting portion, the insert further comprising an adjustment deviceaffixed to the bottom mounting portion for adjusting a placement of aguide pin.
 20. A joint balancing system for balancing the joint duringrepair of the joint including the insert of claim 15, the jointbalancing system further comprising: a first bone angle sensor foraffixing to the tibia during repair of the joint; a second bone anglesensor for affixing to the femur during repair of the joint; and aninsert angle sensor coupled to the insert.